Curable silicone compositions, electrically conductive silicone adhesives, methods of making and using same, and electrical devices containing same

ABSTRACT

A curable silicone composition comprising a curable organosiloxane composition, copper-silver (Cu—Ag) core-shell particles, and hydrocarbon vehicle; the curable silicone composition being characterizable by: a concentration of the Cu—Ag core-shell particles of from 70 to 89 weight percent and a total concentration of silver of from 7.0 to 14 weight percent, all based on weight of the curable silicone composition; wherein the composition remains curable to an electrically conductive silicone adhesive having a volume resistivity of less than 0.020 Ohm-centimeter measured according to Volume Resistivity Test Method.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage filing under 35 U.S.C. §371 ofPCT Application No. PCT/US14/25149 filed on 13 Mar. 2014, currentlypending, which claims the benefit of U.S. Provisional PatentApplications No. 61/782,078 filed 14 Mar. 2013 and No. 61/906,458 filed20 Nov. 2013, both under 35 U.S.C. §119 (e). PCT Application No.PCT/US14/25149 and U.S. Provisional Patent Applications Nos. 61/782,078and 61/906,458 are hereby incorporated by reference.

Inventions described herein include curable silicone compositions,electrically conductive silicone adhesives, methods of making and usingthe compositions and adhesives, and electrical devices containing thecompositions and adhesives.

One approach to electrically interconnecting components of an electricaldevice is to use an electrically conductive adhesive (ECA). The ECAbinds the components together and facilitates transfer of electriccurrent between them via the ECA during operation of the electricaldevice. A wide variety of electrical components could employ ECAs.

An ECA generally comprises electrically conductive metal particlesdispersed in a non-conductive binder matrix at a concentration abovetheir percolation threshold. Percolation threshold is the minimumconcentration of the metal particles in the ECA that is necessary forconduction of electric current through the ECA. Just below thepercolation threshold, a distinct cutoff of electric current is reached.The cutoff is at a concentration of metal particles that no longer forma continuous path for the current through the binder matrix.

In addition, the ECA should have a volume resistivity compatible withits application. Volume resistivity (ρ) quantifies how strongly amaterial opposes the flow of electric current therethrough.

To achieve acceptable electrical performance, the electricallyconductive metal particles in most ECAs are highly electricallyconductive particles, especially finely divided solids of silver. Gold,and sometimes the less conductive aluminum, may be useful in someapplications. Copper is disfavored for its tendency to spontaneouslyoxidize in air, which makes copper unsuitable for applications involvingair and heat.

Silver-based curable silicone precursor compositions typically have aminimum of 70 weight percent (wt %) of silver for satisfactoryelectrical performance. Reducing the concentration of silver, which isexpensive, below that minimum has led in the past to an unsatisfactorygain in volume resistivity.

Artisans have made different curable precursor compositions and ECAs.Examples of curable precursor compositions and ECAs are mentioned inU.S. Pat. No. 5,075,038 to R. L. Cole et al; U.S. Pat. No. 5,227,093 toR. L. Cole et al.; JP 2004-027134 A to S. Miyazaki; U.S. Pat. No.8,044,330 B2 to A. Inaba; and WO 2011/101788 A1 to Kleine Jäger, et al.

Preparation of Cu—Ag core-shell particles are mentioned by Hai, H. T. etal., Oxidative Behavior of Cu—Ag Core-Shell Particles for Solar CellApplications, 2013, doi: http://dx.doi.org/10.1016/j.jallcom.2013.02.048(Journal of Alloys and Compounds). Kim S. J., et al. mention sinteredCu—Ag core-shell nanoparticles in Fabrication of conductiveinterconnects by Ag migration in Cu—Ag core-shell nanoparticles, AppliedPhysical Letters, 2010; 96:144101-1 to 144101-3. These references do notdisclose any ECA containing Cu—Ag core-shell particles or a polymercomposition containing unsintered Cu—Ag core-shell particles.

We (the present inventors) found problems with prior art curableprecursor compositions and resulting ECAs. For instance, the prior artdoes not teach how to achieve a curable precursor composition whereintotal concentration of silver in the composition is extremely low, e.g.,below 15 wt % and the volume resistivity of the resulting ECA ismaintained below 0.020 Ohm-centimeter. The prior art also does not teachhow to employ Cu—Ag core-shell particles while avoiding the reportedoxidation of the copper(0) of the Cu—Ag core-shell particles when theparticles are exposed to heated air and/or damp conditions (e.g.,relative humidity >50%), such as is commonly used during manufactureand/or use of photovoltaic cell modules.

Also, we found that curable precursor compositions with metal particlesas the only solid filler may have too low viscosity and exhibit too muchslump, bleeding, dripping, and/or filler settling during screen printingthereof.

Our efforts to solve the foregoing concentration and/or oxidationproblems led us to an improved curable silicone compositions andsilicone ECAs and one or more technical solutions of the foregoingproblems that we believe are not disclosed, taught or suggested by theaforementioned art. We believe that attempting to solve the foregoingtechnical problems with only knowledge of the prior art as a whole wouldnot result in the present invention without an inventive or nonobviousstep.

BRIEF SUMMARY OF THE INVENTION

The present invention includes curable silicone compositions,electrically conductive silicone adhesives, methods of making and usingthe compositions and adhesives, and electrical devices containing thecompositions and adhesives. Embodiments include:

A curable silicone composition comprising a curable organosiloxanecomposition, copper-silver (Cu—Ag) core-shell particles, and hydrocarbonvehicle; the curable silicone composition being characterizable by: aconcentration of the Cu—Ag core-shell particles of from 70 to 89 weightpercent and a total concentration of silver of from 7 to 14 weightpercent, all based on weight of the curable silicone composition; andwherein the composition remains curable to an electrically conductivesilicone adhesive having a volume resistivity of less than 0.020Ohm-centimeter measured according to Volume Resistivity Test Method.

An electrically conductive silicone adhesive (ECSA) composition that isa product of curing the curable silicone composition and ischaracterizable by a volume resistivity of less than 0.0010Ohm-centimeter measured according to Volume Resistivity Test Method.

An electrical device comprising first and second electrical componentsand the electrically conductive silicone adhesive.

A method of manufacturing the electrical device.

The invention may be used in electrical components, end-user devices,and methods of their manufacture.

DETAILED DESCRIPTION OF THE INVENTION

The Summary and Abstract are incorporated here by reference. The presentinvention provides the curable precursor composition, the electricallyconductive silicone adhesive (ECSA), the electrical device, and themethod of manufacturing the electrical device.

“May” confers a choice, not an imperative. “Optionally” means is absent,alternatively is present. “Contact” comprises effective touching, e.g.,as for facilitating reaction. The contact may be direct touching. Anyreference herein to a Group or Groups of elements or the Periodic Tableof the Elements means those of the 2011 edition of the Periodic Table ofthe Elements promulgated by IUPAC (International Union of Pure andApplied Chemistry). Unless indicated otherwise by specific statement orcontext (e.g., salt or chelate), any reference to a metal, metal alloy,or metal blend herein refers to the metallic (non-ionic, formaloxidation state 0) form of the relevant element. All “wt %” (weightpercent) are, unless otherwise noted, based on total weight of theingredients used. Ingredients of each composition, mixture, or othermaterial add up to 100 wt %. Any Markush group comprising a genus andsubgenus therein includes the subgenus in the genus, e.g., in Markushgroup “R is hydrocarbyl or alkenyl,” R may be alkenyl, alternatively Rmay be hydrocarbyl, which includes, among other subgenuses, alkenyl.

As used herein, volume resistivity (ρ) and electrical conductivity (κ)refer to bulk volume resistivity and bulk electrical conductivity. If avolume resistivity value and electrical conductivity value inadvertentlyconflict, the volume resistivity value controls. Unless it is indicatedotherwise herein, all volume resistivity values are measured accordingto Volume Resistivity Test Method described later.

The curable silicone composition comprises the curable organosiloxanecomposition, copper-silver (Cu—Ag) core-shell particles, and hydrocarbonvehicle. A de minimis amount of free Ag particles may be present in thecurable silicone composition and/or ECSA as a result of a sloughing offof bits and pieces of the Ag shell from the Cu—Ag core-shell particlesduring preparation and/or use of the curable silicone composition and/orECSA. The curable silicone composition contains less than 2 wt %,alternatively <1 wt %, alternatively <0.5 wt %, alternatively <0.1 wt %,alternatively 0.0 wt % free Ag particles. Similarly, the curablesilicone composition contains less than 2 wt %, alternatively <1 wt %,alternatively <0.5 wt %, alternatively <0.1 wt %, alternatively 0.0 wt %Au particles. The curable silicone composition may lack both free Agparticles and Au particles.

The curable silicone composition may lack an organic material or sourceof oxygen that would otherwise oxidize Cu(0) at 200° C. The curablesilicone composition may lack an epoxy material, a polyimide material,or both. Alternatively, the curable silicone composition may lack anyorganic polymer, which includes the epoxy and polyimide materials.

The curable silicone composition may be curable at a temperature lessthan or equal to 160° C. For example, the curable silicone compositionmay be curable at a temperature of from 20° to 160° C., alternativelyfrom 30° to 155° C., alternatively from 40° C. to 150° C. For example,the curable silicone composition may be curable at a temperature of<130° C., alternatively <120° C., alternatively <100° C., alternatively<80° C., alternatively <75° C.; and at a temperature of >20° C.,alternatively >25° C., alternatively >30° C., alternatively >40° C.Advantageously, the curable silicone composition may be curable undercuring conditions comprising an air atmosphere at ambient pressure(e.g., at 101 kilopascals pressure) and any one of the aforementionedtemperatures such that the curing conditions do not materially result inoxidation of copper(0) of the Cu core, alternatively minimize oxidationof copper(0) of the Cu core such that the resulting ECSA has the volumeresistivity of less than 0.020 Ohm-centimeter. Alternatively, thecurable silicone composition may be curable under vacuum or under aninert gas atmosphere at ambient pressure and any one of theaforementioned temperatures. The inert gas atmosphere may be a gas ofmolecular nitrogen, helium, or argon.

The curable silicone composition may be a curable silicone compositioncomprising a blend of the following ingredients: a hydrocarbon vehicle,wherein the hydrocarbon vehicle is characterizable by a boiling pointfrom 100 to 360 degrees Celsius; a curable organosiloxane composition;and Cu—Ag core-shell particles; wherein the total concentration ofsilver is <15 wt % based on weight of the curable silicone composition.The curable silicone composition may alternatively further comprise amechanical thixotropic filler (MTF), which may beneficially function toproduce an embodiment of the curable silicone composition having aThixotropic Index (η₁/η₁₀) of from 3 to 10. Thixotropic Index (η₁/η₁₀)is measured according to the method described later. Such compositionshaving Thixotropic Index (η₁/η₁₀) of from 3 to 10 are printable. Thecomposition remains curable to an electrically conductive siliconeadhesive having a volume resistivity of less than 0.0010 Ohm-centimeter.

For example the curable silicone composition may comprise a blend of thefollowing ingredients: a hydrocarbon vehicle at a concentration of from4 to 20 wt % based on weight of the curable silicone composition,wherein the hydrocarbon vehicle is characterizable by a boiling pointfrom 100 to 360 degrees Celsius; a curable organosiloxane composition ata concentration of from 7 to 25 wt % based on weight of the curablesilicone composition; and Cu—Ag core-shell particles at a concentrationof from 70 to 89 wt % based on weight of the curable siliconecomposition; wherein the total concentration of silver is from 7 to 14wt % based on weight of the curable silicone composition. Thecomposition remains curable to an electrically conductive siliconeadhesive having a volume resistivity of less than 0.020 ohm-centimeter(Ohm-cm).

The curable silicone composition may be characterizable by (i.e., may becurable to an ECSA having) a volume resistivity less than 0.010 Ohm-cm,alternatively <0.0010 Ohm-cm, alternatively <0.00090 Ohm-cm,alternatively <0.00080 Ohm-cm, alternatively <0.00070 Ohm-cm,alternatively <0.00060 Ohm-cm, alternatively <0.00050 Ohm-cm,alternatively <0.00040 Ohm-cm. The volume resistivity is >0 Ohm-cm,e.g., 0.00001 Ohm-cm. While typically the lower the volume resistivityof the ECSA the better, in some embodiments the volume resistivity maybe >0.00001 Ohm-cm, alternatively >0.00005 Ohm-cm,alternatively >0.00009 Ohm-cm, alternatively >0.00010 Ohm-cm,alternatively >0.00020 Ohm-cm, alternatively >0.00030 Ohm-cm.

The hydrocarbon vehicle is a liquid collection of molecules wherein eachmolecule consists of carbon and hydrogen atoms, including one or morethan one isotopic forms of carbon and hydrogen atoms, respectively. Eachmolecule has carbon-carbon bonds wherein each carbon-carbon bondindependently is a single, double, triple, or aromatic bond. Eachmolecule independently may be a saturated hydrocarbon, unsaturatedhydrocarbon, aromatic hydrocarbon, or a combination of any two or threethereof. Each molecule independently may be acyclic or cyclic, or acombination of acyclic and cyclic portions. Each acyclic molecule orportion independently may be branched or unbranched. Each cyclicmolecule or portion independently may be aromatic or non-aromatic.Additionally, each cyclic molecule or portion independently may bemonocyclic or polycyclic, including bicyclic or tricyclic. Eachpolycyclic molecule or portion may be simple (separate rings that do notshare atoms) or complex (having at least two rings that share at leastone atom). Examples of complex polycyclic molecules are bridged,spirocyclic, and fused polycyclic. Each ring of the polycyclic moleculeindependently may be aromatic or non-aromatic. The hydrocarbon vehiclemay be from any one or more of the following classes: alkane, alkene,alkyne, cycloalkane, cycloalkene, cycloalkyne, and aromatichydrocarbons. The hydrocarbon vehicle may be a mixture of any two ormore hydrocarbons of the same or different classes. The mixture ofhydrocarbons of the same class may be a mixture of alkanes such as amixture of unbranched alkanes (normal-alkanes) or a mixture of branchedalkanes (e.g., an isoalkanes mixture, neo-alkanes mixture, ortertiary-alkanes mixture). For example, the isoalkanes mixture maycomprise at least two of (C₉-C₁₂)isoalkanes, at least two of(C₁₂-C₁₆)isoalkanes or at least two of (C₁₆-C₂₂)isoalkanes. The mixtureof hydrocarbons from different classes may be a mixture of alkanes andaromatic hydrocarbons or a mixture of alkanes and alkenes.

The hydrocarbon vehicle is also characterizable by a boiling point of atleast 100 degrees Celsius (° C.), alternatively from 100 to 360° C. Theparticular boiling point of the hydrocarbon vehicle is not critical solong as it is above 100° C. and yet not so high that the hydrocarbonvehicle could not be substantially removed during curing of the curablesilicone composition and/or thereafter. “Substantially removed” meansremoval of at least 50 volume percent (vol %), alternatively at least 75vol %, alternatively at least 90 vol %, alternatively at least 98 vol %,alternatively at least 99 vol % removed, based on starting volume of thehydrocarbon vehicle and an amount such that the ECSA has <5 wt %,alternatively <4 wt %, alternatively <3 wt %, alternatively <2 wt %,alternatively <1 wt % of hydrocarbon vehicle after curing has beenstopped or completed. The amount of hydrocarbon vehicle remaining in theECSA after curing may be equal to the weight of the hydrocarbon vehicleused in the curable silicone composition minus the weight lost duringcuring. The weight lost during curing may equal the weight of thecurable silicone composition before curing minus the weight of the ECSA.Alternatively, thermal gravimetric analysis (TGA) may be employed tomeasure weight change upon heating and pyrolysis gas chromatograph-massspectrometry may be employed to quantitatively analyze (identify andquantify) materials that have left the curable silicone composition orECSA prepared therefrom during curing of the former. The hydrocarbonvehicle can be removed without degrading the ECSA to a degree ofdecomposition whereat the ECSA would not be able to meet its electrical,adhesive, or both limitations described herein.

Additionally, an embodiment of the hydrocarbon vehicle with a particularboiling point or boiling point range may be used to accommodatebeneficial curing conditions for curing the curable siliconecomposition. For example, the boiling point or boiling point rangetemperature range may beneficially facilitate shrinkage of volume ofmaterial during curing such that the volume of the curable siliconecomposition immediately prior to curing is higher than the volume of theresulting ECSA after curing. The shrinkage may advantageously be at arelatively slow and steady rate such that packing of the electricallyconductive filler in the curable silicone composition is improved,resulting in lower volume resistivity and higher electrical conductivityof the ECSA than would be obtained with a comparative ECSA having ahydrocarbon vehicle having a boiling point less than 100° C., especiallyless than 80° C., alternatively <60° C., alternatively <50° C. The rateof shrinkage may be adjusted to improve packing of the electricallyconductive filler in the ECSA.

For most applications, a maximum boiling point (i.e., an end boilingpoint) of 360° C. is sufficient for the hydrocarbon vehicle. When thehydrocarbon vehicle is a mixture of different hydrocarbon molecules, thehydrocarbon vehicle may be characterizable by an initial boiling pointof lowest boiling molecules and an end boiling point of highest boilingmolecules. For example, the hydrocarbon vehicle may have an initialboiling point greater than 150° C. and an end boiling less than 300° C.;alternatively an initial boiling point of greater than 210° C. and anend boiling point of less than 270° C.; alternatively an initial boilingpoint of >160° C. and an end boiling point <205° C.; alternatively aninitial boiling point of >210° C. and an end boiling point <270° C.;alternatively an initial boiling point of >270° C. and an end boilingpoint <355° C.

The hydrocarbon vehicle may be present in the curable siliconecomposition at a concentration of from 4 to 25 wt %, alternatively from4 to 15 wt %, alternatively from 4.5 to 15 wt %, alternatively from 4.5to 12 wt %, all based on total weight of the curable siliconecomposition.

The “copper-silver core-shell particles” or Cu—Ag core-shell particlesmean a finely divided composite having an inner part and an outer layer,wherein the inner part (core) is a solid form of the element havingatomic number 29 (Cu) and wherein the outer layer (shell) is a solidform of the element having atomic number 47 (Ag). The concentration ofthe Cu—Ag core-shell particles in the curable silicone composition maybe from 70 to 89 wt %, alternatively from 75 to 89 wt %, alternativelyfrom 79.5 to 86.4 wt %, alternatively from 79.9 to 86.0 wt %, all basedon weight of the curable silicone composition.

The Ag shell covers some, alternatively most, alternatively all of theCu core. Even when the Ag shell does not cover all of the Cu core, theAg shell covers enough of the Cu core such that the volume resistivityof the ECSA may be maintained below 0.020 Ohm-cm, alternatively <0.0010Ohm-cm. The Ag shell may cover a substantial portion of the Cu core suchthat oxidative stability of the copper (0) of the core during curing ofthe curable silicone composition and/or during use of the resulting ECSAmay be maintained. The Cu—Ag core-shell particles may be unsintered,thereby allowing the curable organosiloxane composition of the curablesilicone composition, and the cured binder matrix resulting from curingthereof, to surround and encapsulate an agglomeration of the Cu—Agcore-shell particles, thereby inhibiting contact of ambient molecularoxygen with the Cu cores. To achieve this protection of the Cu coresfrom oxidation, it is not necessary for the curable organosiloxanecomposition, and the resulting cured binder matrix, to surround andencapsulate each Cu—Ag core-shell particle. In some locations on theCu—Ag core-shell particles in the curable silicone composition and ECSA,there may be direct physical touching between such Cu—Ag core-shellparticles. There may also be some voids or gas pockets between the Cu—Agcore-shell particles where air or other gaseous atmosphere (e.g., inertgas) may have been trapped during preparation of the curable siliconecomposition and/or ECSA.

Alternatively, even where some of the exposed Cu(0) of the cores isoxidized during the curing of the curable silicone composition or use ofthe resulting ECSA, the concentration of Ag in the Cu—Ag core-shellparticles may be sufficient for the volume resistivity of the ECSA to bemaintained below 0.020 Ohm-cm, alternatively <0.0010 Ohm-cm viaelectrical conduction through a continuous path through the ECSA via theAg shells. Therefore, the Cu cores may be substantially electricallyconductive as for Cu(0); the Cu cores may be oxidized to Cu oxides atleast exposed surfaces thereof such that the electrical conductivity ofthe Cu cores is significantly decreased compared to that for Cu(0) onlycores; or the electrical conductivity of the Cu cores may have anintermediate status in between these two characteristics.

The concentration of silver in the Cu—Ag core-shell particles may befrom 5 to 20 wt %, alternatively from 6 to 18 wt %, alternatively from 8to 16 wt %, alternatively from 9 to 14 wt % (e.g., 9 wt %, 10 wt %, 11wt %, or 12 wt %), all based on weight of the Cu—Ag core-shellparticles.

Total concentration of silver in the curable silicone composition may be14 wt % or less, alternatively <14 wt %, alternatively <13 wt %,alternatively <12 wt %. Total concentration of silver in the curablesilicone composition may be at least 6.5 wt %, alternatively at least 7wt %, alternatively >7 wt %, alternatively at least 8 wt %,alternatively >8 wt %. For example, the total silver concentration maybe from 7 to 14 wt %, alternatively from 7.0 to 12 wt %, alternativelyfrom 7.1 to 12 wt %, alternatively from 7.5 to 12 wt %, alternativelyfrom 8.5 to 11 wt %.

The Cu—Ag core-shell particles may be in the shape of cuboidals, flakes,granules, irregulars, rods, needles, powders, spheres, or a mixture ofany two or more of cuboidals, flakes, granules, irregulars, rods,needles, powders, and spheres. Typically, the Cu—Ag core-shell particleshave a median particle size of from 0.5 to 20 microns, alternativelyfrom 1 to 15 microns, alternatively from 2 to 10 microns. The particlesizes may be determined by particle size distribution analysis andreported as a median particle size in μm (D<50), alternatively as thediameter in μm below which 10% (D10), 50% (D50) and 90% (D90) of thecumulative particle size distribution is found. Prior to preparing thecurable silicone composition, the particle size may be determined with asample of Cu—Ag core-shell particles in dry form or dispersed in adispersant (e.g., water) using laser diffraction or particle sizeanalyzer instrument. For example, the MALVERN MASTERSIZER S particlesize analyzer instrument (Malvern Instruments, Malvern, Worcestershire,UK) may be used with particles having a size in the range of from 300 nmto 1000 μm; and the MICROTRAC NANOTRAC UPA150 particle size analyzerinstrument (Microtrac, Inc., Montgomeryville, Pa., USA) may be used withparticles having a size in the range of from 5 nm to 4 μm. Atomic forcemicroscopy (AFM), scanning electron microscopy (SEM) or transmissionelectron microscopy (TEM) may be used to measure the particle sizes ofCu—Ag core-shell particles after the particles have been dispersed inthe curable silicone composition or after curing same to the ECSA.Unless stated otherwise herein, any particle size measurement is forparticles prior to preparing the curable silicone composition containingsame.

The Cu—Ag core-shell particles may be surface treated. For example, suchparticles may be surface treated to improve “wetability” by the curableorganosiloxane composition and/or dispersability in the curable siliconecomposition, ECSA, or both. The surface treatment may comprisecontacting the particles with a chemical substance such as an acid,base, compatibilizer, lubricant, or processing aid. The chemicalsubstance may be aqueous sodium hydroxide, a (C₄-C₂₈)carboxylic acid orester (e.g., a fatty acid or fatty acid ester), the hydrocarbon vehicle,a silicon-containing compound, or sulfuric acid. The silicon-containingcompound may be an organochlorosilane, organosiloxane, organodisilazane,organoalkoxysilane. The lubricant may be used to treat the Cu—Agcore-shell particles during a milling process of making Cu—Ag core-shellflakes from Cu—Ag core-shell powder to prevent the Cu—Ag core-shellpowder from cold welding or forming agglomerates. The chemical substancemay, alternatively may not, be removed from the Cu—Ag core-shellparticles before the particles are mixed with other ingredients of thecurable silicone composition. Even if the treated particles are washedwith solvent after the treating process, some chemical substances suchas the lubricant or compatibilizer may remain chemisorbed on the surfaceof the particles.

The “mechanical thixotropic filler” or MTF is any finely divided solidlacking electrically conductive metal and that modulates the ThixotropicIndex (η₁/η₁₀) without increasing volume resistivity of the curablesilicone composition above 0.020 Ohm-cm, alternatively >0.0010 Ohm-cm,or any one of the other aforementioned volume resistivity values.Examples of the MTF are carbon nanotubes; electrically non-conductivefiller particles; or a combination of any two or more of the carbonnanotubes and electrically non-conductive filler particles. In thecurable silicone composition, the MTF, when present, is at a totalconcentration of from 0.1 to 5 wt %, alternatively from 0.2 to 2 wt %,alternatively from 0.2 to 2.0 wt %, alternatively from 0.5 to 1.5 wt %,alternatively from 0.50 to 1.5 wt %, all based on weight of the curablesilicone composition.

The carbon nanotubes used in the present invention may be single-walledcarbon nanotubes; multi-walled carbon nanotubes; derivatizedsingle-walled carbon nanotubes; derivatized multi-walled carbonnanotubes; or a mixture of any two or more of the single-walled carbonnanotubes, multi-walled carbon nanotubes, derivatized single-walledcarbon nanotubes, and derivatized multi-walled carbon nanotubes. Thecarbon nanotubes may be characterizable by an electrical conductivity(κ) of ≧1 S/m. The MTF may consist of carbon nanotubes. The“single-walled carbon nanotube” (SWCNT) is an allotrope of carbon havingsingle cylindrical structure (i.e., cylindrical graphene). The“multi-walled carbon nanotubes” (MWCNT) is an allotrope of carbon havingmultiple sheets of graphite (graphene sheets) in form of coaxial(concentric) cylindrical structures (cylinder within cylinder (“RussianDoll model”)) or having a single sheet of graphite (graphene sheet)rolled around itself to form a rolled scroll-like structure (“Parchmentmodel”), or a combination thereof. The CNT may or may not have a“bamboo-like” structure, which may be prepared by chemical vapordeposition pyrolysis of melamine under argon atmosphere at 800° to 980°C. The “derivatized carbon nanotube” is a graphenated carbon nanotube, afunctional group-containing carbon nanotube, or a combination structurethereof. The functional group-containing CNT has at least oneheteroatom-containing moiety that is covalently bonded to a carbon atomof the carbon nanotube wall wherein the moiety has at least oneheteroatom that is O, N, S, P, or halogen (F, Cl, Br, or I). Examples ofsuch functional groups are —NO₃, —SO₃H, —PO₃H, —OH, —COOH, and —NH₂. The“graphenated carbon nanotube” is a hybrid structure comprising agraphitic foliate covalently bonded to a sidewall of a SWCNT or MWCNT.The functional group-containing carbon nanotubes may be obtained from acommercial supplier thereof or prepared according to any suitablemethod. Examples of the suitable method comprise exposing a startingcarbon nanotube with a chemical substance, an environmental condition,or any combination thereof so as to install the at least one functionalgroup on a carbon atom of the starting carbon nanotubes to give thefunctional group-containing carbon nanotubes. The chemical substance maybe an aqueous base such as aqueous sodium hydroxide; aqueous acid suchas sulfuric acid, nitric acid, or a mixture thereof; an oxidant (e.g.,oxygen gas); or a mixture thereof. The environmental condition may beheat treatment (e.g., 900° to 1,100° C. for from 1 to 60 minutes), inertatmosphere, or any combination thereof. graphenated carbon nanotube maybe obtained from a commercial supplier thereof or prepared according toany suitable method. Examples of the suitable method comprise any one ofthe methods of Yu, K., et al. (Carbon Nanotube with Chemically BondedGraphene Leaves for Electronic and Optoelectronic Applications, J. Phys.Chem. Lett., 2011; 13 (2): 1556-1562); Stoner, B. R. et al. (Graphenatedcarbon nanotubes for enhanced electrochemical double layer capacitorperformance, Appl. Phys. Lett., 2011; 99 (18):183104-1 to 183104-3); andHsu, H-C et al. (Stand-up structure of graphene-like carbon nanowalls onCNT directly grown on polyacrylonitrile-based carbon fiber paper assupercapacitor, Diamond and Related Materials, 2012; 25:176-179).Examples of the combination structure are —NO₃, —SO₃H, —PO₃H, —OH,—COOH, or —NH₂ functionalized graphenated carbon nanotubes such aswherein the —NO₃, —SO₃H, —PO₃H, —OH, —COOH, or —NH₂ groups comprise from0.01 to 5 wt %, alternatively from 0.1 to 3 wt %, alternatively from 0.5to 2 (e.g., 1 wt %) of the weight of the combination structure.

Each of the different types of carbon nanotubes particles independentlymay be characterizable by a maximum outer diameter of 10 μm,alternatively 1 μm, alternatively 500 nm, alternatively 300 nm,alternatively 200 nm, alternatively 100 nm, alternatively 50 nm; and aminimum outer diameter of 1 nm, alternatively 2 nm, alternatively 5 nm,alternatively 8 nm, alternatively 10 nm, alternatively 15 nm,alternatively 25 nm. The carbon nanotubes particles may becharacterizable by a maximum length of 1 mm, alternatively 500 μm,alternatively 300 μm, alternatively 150 μm, alternatively 100 μm,alternatively 50 μm, alternatively 25 μm; and a minimum length of 0.1μm, alternatively 1 μm, alternatively 5 μm., alternatively 10 μm,alternatively 20 μm. Raman spectroscopy, AFM, SEM or TEM may be used tomeasure the diameter and length.

The carbon nanotubes may be dispersed in the curable organosiloxanecomposition of the curable silicone composition by any suitable meanssuch as mixing, sonication, or a combination thereof. The concentrationof the carbon nanotubes, when present, in the curable siliconecomposition may be from 0.1 to 5 wt % (e.g., an embodiment of aspect 1described later), alternatively from 0.1 to 5.0 wt %, alternatively from0.2 to 2 wt %, alternatively from 0.5 to 1.5 wt %, alternatively from0.50 to 1.2 wt %, all based on weight of the curable siliconecomposition. Advantageously, the concentration of the carbon nanotubes,when present, in the curable silicone composition may be varied withinthe foregoing ranges to adjust rheology such as thixotropic index whilebeneficially maintaining volume resistivity of the resulting ECSA below0.020 Ohm-cm, alternatively <0.0010 Ohm-cm, or any one of the otheraforementioned volume resistivity values, without adding gold oraluminum (whether discrete elements or in metal alloys or blends); andwhile maintaining the total concentration of silver in the attractiverange of <15 wt % in the curable silicone composition.

The “electrically conductive metal” means an element of any one ofGroups 1 to 13 of the Periodic Table of the Elements plus tin, and leadfrom Group 14, antimony from Group 15, bismuth from Group 16, andlanthanides and actinides, or a metal alloy of any two or more suchelements. The element or metal alloy may have a volume resistivity (ρ)at 20° C. less than 0.0001 Ohm-cm and an electrical conductivity (κ) at20° C. greater than 1×10⁶ S/m. Examples of such elements are silver,copper, gold, aluminum, calcium, molybdenum, zinc, bismuth, indium,lithium, tungsten, nickel, iron, palladium, platinum, tin, lead,titanium, mercury, and blends thereof. Examples of such metal alloys arebrass (a metal alloy of copper and zinc), bronze (a metal alloy ofcopper and tin), 67Cu33Zn, carbon steel, grain oriented electricalsteel, MANGANIN (trademark name for a metal alloy of formula Cu₈₆Mn₁₂Ni₂by Isabellenhütte Heusler GmbH & Co. KG, Dillenburg, Germany),constantin (a metal alloy of 55% copper and 45% nickel), nichrome, andblends thereof. The curable silicone composition and ECSA may lack anelectrically conductive metal other than the Cu—Ag core-shell particles.

The “electrically non-conductive filler particles” are finely-dividedsolids having a volume resistivity (ρ) at 20° C. greater than 100 Ohm-cmand an electrical conductivity (κ) at 20° C. less than 1.0 S/m. The MTFmay consist of the electrically non-conductive filler particles. Theelectrically non-conductive filler particles may be silica glass (e.g.,soda-lime-silica glass or borosilicate glass), diamond polymorph ofcarbon, silica, organic polymer, organosiloxane polymer, or a ceramic.The electrically non-conductive filler particles are distinct from theaforementioned electrically conductive metals. The electricallynon-conductive filler particles may have sufficient size to improvepacking of the Cu—Ag core-shell particles in the ECSA such that the ECSAhas lower volume resistivity than that of a comparative ECSA having thesame concentration of electrically non-conductive filler particleshaving smaller size. Such sufficient size may be an average particlediameter of the electrically non-conductive filler particles greaterthan average particle diameter of the silver filler. Spherical silicaglass filler particles may beneficially enhance (i.e., decrease) volumeresistivity of the resulting ECSA compared to that of an ECSA preparedfrom an identical curable silicone composition except lacking thespherical silica glass filler particles. Alternatively or additionally,the spherical silica glass filler particles may beneficially helpmaintain thickness uniformity of a bondline of the curable siliconecomposition, ECSA, or both, wherein the bondline has been disposed on asubstrate such as a substrate for an electrical component, and theresulting component experiences above ambient temperature, pressure, orboth (e.g., as during a laminating step). Alternatively or additionally,the spherical silica glass filler particles may beneficially penetrateor mechanically abrade away a metal oxide layer (e.g., copper oxidelayer) that may have been formed on an exterior surface of a substrateprone to oxidation or on an exposed surface of the Cu core of the Cu—Agcore-shell particles. An example of the substrate prone to oxidation isa copper foil or wire, a surface layer of which copper may spontaneouslyoxidize in air to form a copper oxide layer. The curable siliconecomposition and ECSA may lack, alternatively may further comprise, theelectrically non-conductive filler particles. The concentration of theelectrically non-conductive filler particles, when present, may be from0.01 to 5 wt %, alternatively from 0.1 to 2 wt %, alternatively from 0.1to 1 wt %, all based on weight of the curable silicone composition.

The electrically non-conductive filler particles may be in the shape ofcuboidals, flakes, granules, irregulars, needles, powders, rods,spheres, or a mixture of any two or more of cuboidals, flakes, granules,irregulars, needles, powders, rods, and spheres. The particles may havea median particle size of from 5 to 100 μm. The particles may becharacterizable by a maximum particle size of 1 millimeter,alternatively 100 microns (μm), alternatively 50 μm, alternatively 10μm, alternatively 1 μm, alternatively 500 nanometers (nm). Particle sizemay be measured as described before for measuring Cu—Ag core-shellparticle size.

The “curable organosiloxane composition” may be any curableorganosiloxane such as a condensation curable organosiloxane, freeradical curable organosiloxane, or hydrosilylation-curableorganosiloxane. The “silicone” includes linear and branchedorganosiloxanes. The main advantages of the present invention may beachieved with embodiments employing any curable organosiloxane.

Depending on its reactive functional groups, curing or rate of curing ofthe curable organosiloxane composition may be enhanced by contacting thecurable organosiloxane composition with a metal-containing catalyst,heat, ultraviolet (UV) light, O₂, peroxides, water (e.g., water vapor inair), or a combination thereof. The metal of the metal-containingcatalyst may be Sn, Ti, Pt, or Rh. The condensation curableorganosiloxane may be hydroxy-functionalized and/oralkoxy-functionalized. Curing or curing rate of the condensation curableorganosiloxane may be enhanced by moisture, heat, or heat and moisture.The free radical curable organosiloxane may be alkenyl-functionalized(e.g., vinyl) and/or alkynyl-functionalized. Curing or curing rate ofthe free radical curable organosiloxane may be enhanced by UV light orperoxides, heat, or both. The hydrosilylation-curable organosiloxane maybe alkenyl functionalized (e.g., vinyl) and Si—H functionalized. Curingor curing rate of the hydrosilylation-curable organosiloxane may beenhanced by a hydrosilylation catalyst (e.g., a Pt catalyst), heat, orboth hydrosilylation catalyst and heat. Enhancing curing or rate ofcuring may comprise increasing extent or degree of curing or increasingthe rate of curing at a given temperature or decreasing the temperatureat which a given rate of curing is achieved.

Each organosiloxane molecule comprises silicon, carbon, hydrogen, andoxygen atoms. As used in “organosiloxane” the term “organo” means ahydrocarbyl, heterohydrocarbyl, or organoheteryl, which groups arecollectively referred to herein as organogroups. Each organogroup may beheterohydrocarbyl, alternatively organoheteryl, alternativelyhydrocarbyl. The hydrocarbyl, heterohydrocarbyl, and organoheterylgroups are described later. Each organogroup may have from 1 to 20carbon atoms, e.g., a (C₁-C₂₀)hydrocarbyl. Each organosiloxane moleculemay contain only unsubstituted hydrocarbyl groups (i.e., contain onlysilicon, carbon, hydrogen atoms bonded to carbon atoms, and oxygenatoms). Alternatively, one or more organosiloxane molecules may besubstituted with heterohydrocarbyl, organoheteryl, or a reactivefunctional group. Each reactive functional group independently may bethe alkenyl or alkynyl moiety; Si—H moiety; Si—OH moiety; Si—OR^(x)moiety, wherein R^(x) is (C₁-C₁₀)hydrocarbyl, —C(O)(C₁-C₁₀)hydrocarbyl;or —N═CR¹R² moiety, wherein each of R¹ and R² independently is(C₁-C₁₀)hydrocarbyl or R¹ and R² are taken together to form a(C₂-C₁₀)hydrocarbylene.

Each organosiloxane molecule independently may comprise asilicon-containing base polymer having a linear, branched, cyclic, orresinous structure. For example, each silicon-containing base polymerindependently may have a linear structure, alternatively a branchedstructure, alternatively a cyclic structure, alternatively a resinousstructure. Each silicon-containing base polymer independently may be ahomopolymer or copolymer. Each silicon-containing base polymerindependently may have one or more of the reactive functional groups permolecule. At least some, alternatively most, alternatively substantiallyall reactive functional groups react during curing of the curableorganosiloxane composition to give the cured organosiloxane. Thereactive functional groups independently may be located on thesilicon-containing base polymer at terminal, pendant, or terminal andpendant positions. Each organosiloxane molecule of the curableorganosiloxane composition may be a single silicon-containing basepolymer, alternatively may comprise two or more silicon-containing basepolymers differing from each other in at least one of the followingproperties: structure, viscosity, average molecular weight, siloxaneunits, and unit sequence.

The condensation curable organosiloxane may be a diorganosiloxanecompound having on average per molecule at least 1 hydroxyl moiety, or amixture of the diorganosiloxane compound and an organohalogensiliconcompound having on average per molecule at least one halogen atom (e.g.,Cl, F, Br, or I). Alternatively, the condensation curable organosiloxanemay be a mixture of the component (A) and component (B) described inU.S. Pat. No. 6,534,581 B1, at column 3, line 3, to column 4, line 63.(Components (A) and (B) are different than ingredients (A) and (B)described later herein.) The present invention, however, is not limitedto this condensation curable organosiloxane.

As used in “diorganosiloxane compound” (whether condensation curable ornot) the term “diorgano” means a molecule having at least onedifunctional (D) unit of formula R₂SiO_(2/2); wherein each Rindependently is an organogroup. Examples of diorganosiloxane compoundsare a polydimethylsiloxane, wherein each organo group of the D units ismethyl; poly(ethyl,methyl)siloxane wherein the organo groups of the Dunits are methyl and ethyl groups as in the D unit of formulaCH₃(CH₃CH₂)SiO_(2/2); and poly(methyl,phenyl)siloxane wherein the organogroups of the D units are methyl and phenyl groups as in the D unit offormula CH₃(C₆H₅)SiO_(2/2). The diorganosiloxane compound may have all Dunits as in a diorganocyclosiloxane compound. Typically, thediorganosiloxane compound further has at least one M, Q, and/or T units.The reactive functional group(s) may be on any one or more of the Dunits and/or one or more of any M and/or Q units.

The condensation curable organosiloxane may be a diorganosiloxanecompound having on average per molecule at least 1 alkenyl moiety.Alternatively, the free radical curable organosiloxane may be theoligomer, polymer, or product of curing the polymerizable monomerdescribed in U.S. Pat. No. 7,850,870 B2, at column 5, line 28, to column12, line 9. The present invention, however, is not limited to this freeradical curable organosiloxane.

Typically, the curable silicone composition and its curableorganosiloxane composition comprises the hydrosilylation-curableorganosiloxane and after curing the ECSA comprises an at least partiallyhydrosilylation cured organosiloxane. The present invention, however, isnot limited to using hydrosilylation-curable/cured organosiloxanes.

Before at least partial curing, a first embodiment of thehydrosilylation-curable organosiloxane typically comprises ingredients(A) and (C) when ingredient (A) contains a Si—H moiety. Alternatively asecond embodiment of the hydrosilylation-curable organosiloxanetypically comprises ingredients (A), (B) and (C) when ingredient (A)contains or lacks a Si—H moiety. Ingredients (A) to (C) are: (A) atleast one diorganosiloxane compound having an average of at least oneunsaturated carbon-carbon bonds per molecule; (B) anorganohydrogensilicon compound having an average of at least one Si—Hmoieties per molecule; and (C) a hydrosilylation catalyst. Ingredient(B) may function as a chain extender or crosslinker for extending orcrosslinking ingredient (A).

As used in “organohydrogensilicon compound” (whether hydrosilylationcurable or not) the term “organohydrogen” means a molecule having atleast one difunctional unit of formula RHSi, wherein R independently isan organogroup. When the organohydrogensilicon compound is anorganohydrogensiloxane compound, the molecule has the difunctional (D)unit of formula RHSiO_(2/2); wherein R independently is an organogroup.

During hydrosilylation curing, different molecules of ingredient (A) inthe first embodiment, or ingredients (A) and (B) in the secondembodiment, react together via hydrosilylation to give the at leastpartially hydrosilylation cured organosiloxane. The reaction may givesubstantial curing; alternatively complete curing. The hydrosilylationcured organosiloxane may be substantially cured, alternativelycompletely cured. Substantially cured means a degree of curing that isat least 90 mole %, alternatively at least 95 mole %, alternatively atleast 98 mole % cured based on the limiting ingredient. The degree ofcuring may be determined by Differential Scanning Calorimetry (DSC). Afully cured material would not show an exotherm peak by DSC analysiswhen a sample of the fully cured material is heated during the DSCmeasurement. An uncured material that is capable of curing would show anexotherm peak (e.g., indicative of an exothermic event such as areaction or mixing that generates or releases heat) having a maximumarea for the uncured material by DSC analysis when a sample of theuncured material is heated during the DSC measurement. A partially curedmaterial would show an exotherm peak wherein the area thereof would beintermediate between the area of the exotherm peak for the uncuredmaterial and the 0 area (no exotherm peak) for the cured material. Theproportion of area of the exotherm peak of the partially cured materialcompared to the area of the exotherm peak of the uncured material wouldbe proportional to the percent curing of the partially cured material.Each diorganosiloxane compound and organohydrogensilicon compoundindependently may be the same (i.e., have both Si—H and unsaturatedcarbon-carbon bonds in same molecule), alternatively different. Wheningredients (A) and (B) are the same compound, the curing comprisesintermolecular hydrosilylations and may also comprise intramolecularhydrosilylations. When ingredients (A) and (B) are different compounds,the curing comprises intermolecular hydrosilylations.

Ingredient (A), the at least one diorganosiloxane compound, ishydrosilylation-curable and may include a single diorganosiloxanecompound, or a plurality of different diorganosiloxane compounds. Assuggested in the foregoing paragraph, each diorganosiloxane compound maycontain, alternatively lack a Si—H moiety. Each diorganosiloxanecompound independently may have an average of at least 1,alternatively >1, alternatively ≧2, alternatively ≧3, alternatively ≧5,alternatively ≧10 unsaturated carbon-carbon bonds per molecule. Eachunsaturated carbon-carbon bond independently is C═C (alkenyl) or C≡C(alkynyl). Typically at least one of the unsaturated carbon-carbon bondsis C═C, alternatively all of the unsaturated carbon-carbon bonds areC═C, alternatively at least one of the unsaturated carbon-carbon bondsis C≡C, alternatively all are C≡C, alternatively the unsaturatedcarbon-carbon bonds are a combination of C═C and C≡C. Thediorganosiloxane compound may be an alkynyl siloxane or alkenyl siloxanewherein there are at least one alkynyl or alkenyl groups, respectively,and each of the alkynyl or alkenyl groups may be pending from a carbon,oxygen, or silicon atom. Each alkenyl group independently may have oneor more C═C bonds. Each alkenyl may have one C═C and be a(C₂-C₆)alkenyl, alternatively (C₂-C₄)alkenyl (e.g., vinyl or allyl). TheC═C bond in the alkenyl may be internal as in 5-hexen-1-yl or terminalalkenyl as in H₂C═C(H)—(C₀-C₆)alkylene (H₂C═C(H)—(C₀)alkylene is vinyl).The alkynyl and alkenyl groups independently may be located at anyinterval and/or location in the diorganosiloxane compound such asterminal, pendant, or both terminal and pendant (internal) positions.The diorganosiloxane compound(s) may be a mixture or blend of at leasttwo different diorganosiloxane compounds, so long as ingredient (A) hasthe average of at least one unsaturated carbon-carbon bonds permolecule. The diorganosiloxane compound may be a diorganocyclosiloxanemonomer or a polydiorganosiloxane.

Referring again to ingredient (A), the polydiorganosiloxane may bestraight or branched, uncrosslinked or crosslinked and comprise at leasttwo D units. Any polydiorganosiloxane may further comprise additional Dunits. Any polydiorganosiloxane may further comprise at least one M, T,or Q unit in any covalent combination; alternatively at least one Munit; alternatively at least one T unit; alternatively at least one Qunit; alternatively any covalent combination of at least one M unit andat least one T unit. The polydiorganosiloxane with the covalentcombination may be a DT, MT, MDM, MDT, DTQ, MTQ, MDTQ, DQ, MQ, DTQ, orMDQ polydiorganosiloxane. Ingredient (A) may be a mixture or blend ofpolydiorganosiloxanes, e.g., a mixture of MDM and DT molecules. Knownsymbols M, D, T, and Q, represent the different functionality ofstructural units that may be present in a siloxane (e.g., a silicone),which comprises siloxane units joined by covalent bonds. Themonofunctional (M) unit represents R₃SiO_(1/2); the difunctional (D)unit represents R₂SiO_(2/2); the trifunctional (T) unit representsRSiO_(3/2) and results in the formation of branched linear siloxanes;and the tetrafunctional (Q) unit represents SiO_(4/2) and results in theformation of crosslinked and resinous compositions. The reactivegroup-functional siloxane may be R¹SiO_(3/2) units (i.e., T units)and/or SiO_(4/2) units (i.e., Q units) in covalent combination with R¹R⁴₂SiO_(1/2) units (i.e., M units) and/or R⁴ ₂SiO_(2/2) units (i.e., Dunits). Each “R” group, e.g., R, R¹ and R⁴ independently is hydrocarbyl,heterohydrocarbyl, or organoheteryl, which are collectively referred toherein as organogroups. Each hydrocarbyl, heterohydrocarbyl, andorganoheteryl independently may have from 1 to 20, alternatively from 1to 10, alternatively from 1 to 8, alternatively from 1 to 6 carbonatoms. Each heterohydrocarbyl and organoheteryl independently comprisescarbon, hydrogen and at least one heteroatom that independently may behalo, N, O, S, or P; alternatively S; alternatively P; alternativelyhalo, N, or O; alternatively halo; alternatively halo; alternatively O;alternatively N. Each heterohydrocarbyl and organoheteryl independentlymay have up to 4, alternatively from 1 to 3, alternatively 1 or 2,alternatively 3, alternatively 2, alternatively 1 heteroatom(s). Eachheterohydrocarbyl independently may be halohydrocarbyl (e.g.,fluoromethyl, trifluoromethyl, trifluorovinyl, or chlorovinyl),alternatively am inohydrocarbyl (e.g., H₂N-hydrocarbyl) oralkylaminohydrocarbyl, alternatively dialkylaminohydrocarbyl (e.g.,3-dimethylaminopropyl), alternatively hydroxyhydrocarbyl, alternativelyalkoxyhydrocarbyl (e.g., methoxyphenyl). Each organoheterylindependently may be hydrocarbyl-N(H)—, (hydrocarbyl)₂N—,hydrocarbyl-P(H)—, (hydrocarbyl)₂P—, hydrocarbyl-O—, hydrocarbyl-S—,hydrocarbyl-S(O)—, or hydrocarbyl-S(O)₂—. Each hydrocarbyl independentlymay be (C₁-C₈)hydrocarbyl, alternatively (C₁-C₆)hydrocarbyl,alternatively (C₁-C₃)hydrocarbyl, alternatively (C₁-C₂)hydrocarbyl. Each(C₁-C₈)hydrocarbyl independently may be (C₇-C₈)hydrocarbyl,alternatively (C₁-C₆)hydrocarbyl. Each (C₇-C₈)hydrocarbyl may be aheptyl, alternatively an octyl, alternatively benzyl, alternativelytolyl, alternatively xylyl. Each (C₁-C₆)hydrocarbyl independently may be(C₁-C₆)alkyl, (C₂-C₆)alkenyl, (C₂-C₆)alkynyl, (C₃-C₆)cycloalkyl, orphenyl. Each (C₁-C₆)alkyl independently may be methyl, ethyl, propyl,butyl, or pentyl; alternatively methyl or ethyl; alternatively methyl;alternatively ethyl. Each halo independently may be bromo, fluoro orchloro; alternatively bromo; alternatively fluoro; alternatively chloro.Each R, R¹ and R⁴ independently may be hydrocarbyl; alternativelyhalohydrocarbyl; alternatively hydrocarbyl and at least oneheterohydrocarbyl; alternatively hydrocarbyl and at least oneorganoheteryl. There may be an average of at least 1 “R” per moleculehaving an alkenyl or alkynyl group capable of undergoinghydrosilylation. For example, there may be an average of at most 4,alternatively at least 1, alternatively >1, alternatively at least 2,alternatively 3, alternatively from 1 to 4, alternatively from 1 to 3alkenyl or alkynyl group per diorganosiloxane molecule eachindependently capable of undergoing hydrosilylation. Examples ofsuitable alkenyl are vinyl, fluorovinyl, trifluorovinyl, allyl,4-buten-1-yl, and 1-buten-4-yl. Examples of suitable alkynyl areacetylenyl, propyn-3-yl, and 1-butyn-4-yl.

Referring again to ingredient (A), the polydiorganosiloxane may be apolydialkylsiloxane, e.g., an alkyldialkenylsiloxy-terminatedpolydialkylsiloxane or a dialkylalkenylsiloxy-terminatedpolydialkylsiloxane, e.g., a dialkylvinylsiloxy-terminatedpolydialkylsiloxane. Examples of the dialkylvinylsiloxy-terminatedpolydialkylsiloxane are dimethylvinylsiloxy-terminated polydimethylsiloxane; diethylvinylsiloxy-terminated polydim ethylsiloxane;methyldivinylsiloxy-terminated polydimethylsiloxane;dimethylvinylsiloxy-terminated polydiethylsiloxane;dimethylvinylsiloxy-terminated poly(methyl,ethyl)siloxane;poly(methyl,(C₇-C₈)hydrocarbyl)siloxane; and combinations thereof.Alternatively, the polydiorganosiloxane may be a hydroxy-terminatedpolydiorganosiloxane. The hydroxy-terminated polydiorganosiloxane may bea hydroxy-terminated polydialkylsiloxane having pendent alkenyl, alkynl,or alkenyl and alkenyl groups. Examples of the hydroxy-terminatedpolydialkylsiloxane are hydroxy-terminated polydimethylsiloxane havingpendent vinyl groups; hydroxy-terminated polydiethylsiloxane havingpendent vinyl groups; hydroxy-terminated poly(methyl,ethyl)siloxanehaving pendent vinyl groups; hydroxy-terminatedpoly(methyl,(C₇-C₈)hydrocarbyl)siloxane having pendent vinyl groups; andcombinations thereof. Terminated means mono (alpha), alternatively bis(both alpha and omega) termination. Alternatively, any one of theforegoing polydialkylsiloxanes may further comprise one or more (e.g.,from 1 to 3) internal (alkyl,alkynyl) units, alternatively internal(alkyl,alkenyl) units (e.g., methyl,vinyl or ethyl,vinyl units) or oneor more (e.g., from 1 to 3) alkenyl-containing pendent groups, e.g., adimethylvinylsiloxy-pendent group-containing polydimethylsiloxane.Alternatively, the polydiorganosiloxane may be an alkenyldialkylsilylend-blocked polydialkylsiloxane; alternatively a vinyldimethylsilylend-blocked polydimethylsiloxane. Ingredient (A) may be apolydiorganosiloxane comprising methyl and vinyl R groups. Ingredient(A) may be a poly(methyl,vinyl)siloxane (homopolymer); alternatively ahydroxy-terminated poly(methyl,vinyl)siloxane (homopolymer);alternatively a poly(methyl,vinyl)(dimethyl)siloxane copolymer;alternatively a hydroxy-terminated poly(methyl,vinyl)(dimethyl)siloxanecopolymer; alternatively a mixture of any of at least two thereof. Apoly(methyl,vinyl)(dimethyl)siloxane copolymer means a molecule havingR¹,R⁴SiO_(2/2) units wherein R¹ is methyl and R⁴ is vinyl andR¹,R¹SiO_(2/2) units wherein each R¹ is methyl.

Referring again to ingredient (A), the diorganocyclosiloxane monomer maybe a (R¹,R⁴)cyclosiloxane, wherein R¹ and R⁴ independently are asdefined previously. The (R¹,R⁴)cyclosiloxane may be a(C₇-C₈)hydrocarbyl,alkenyl-cyclosiloxane,(C₇-C₈)hydrocarbyl,alkynyl-cyclosiloxane, alkyl,alkynyl-cyclosiloxane,or a alkyl,alkenyl-cyclosiloxane, wherein (C₇-C₈)hydrocarbyl and alkylindependently are as defined previously. The(alkyl,alkenyl)-cyclosiloxane may be, e.g., a(alkyl,vinyl)-cyclosiloxane, e.g., a methyl,vinyl-cyclosiloxane or(ethyl,vinyl)-cyclosiloxane.

Referring again to ingredient (A), the diorganosiloxane compound mayfurther comprise, alternatively may substantially lack volatilediorganosiloxanes. Reiterated, the diorganosiloxane compound may be usedas prepared, with volatile diorganosiloxane components retained;alternatively the as prepared diorganosiloxane compound may bedevolatilized to remove a volatile fraction before use in the curableorganosiloxane composition.

Referring again to ingredient (A), the diorganosiloxane compound mayhave a number-average molecular weight (M_(n)) of from 500 to 50,000g/mol, alternatively from 500 to 10,000 g/mol, alternatively 1,000 to3,000, g/mol, where the M_(n) is determined by gel permeationchromatography employing a low angle laser light scattering detector, ora refractive index detector and silicone resin (MQ) standards. Thediorganosiloxane compound may have a dynamic viscosity of from 0.01 to100,000 Pascal-seconds (Pa·s), alternatively from 0.1 to 99,000 Pa·s,alternatively from 1 to 95,000 Pa·s, alternatively from 10 to 90,000Pa·s, alternatively from 100 to 89,000 Pa·s, alternatively from 1,000 to85,000 Pa·s, alternatively from 10,000 to 80,000 Pa·s, alternativelyfrom 30,000 to 60,000 Pa·s, alternatively from 40,000 to 75,000 Pa·s.,alternatively from 40,000 to 70,000 Pa·s, alternatively from 10,000 to<40,000 Pa·s, alternatively from 5,000 to 15,000 Pa·s, alternativelyfrom >75,000 to 100,000 Pa·s. The dynamic viscosity is measured at 25°C. according to the dynamic viscosity test method described later. Thediorganosiloxane compound may have less than 10 wt %, alternatively lessthan 5 wt %, alternatively less than 2 wt %, of silicon-bonded hydroxylgroups, as determined by ²⁹Si-NMR. Alternatively, the diorganosiloxanecompound may have less than 10 mole percent (mol %), alternatively lessthan 5 mol %, alternatively less than 2 mol %, of silicon-bondedhydroxyl groups, as determined by ²⁹Si-NMR.

The ingredient (A) (e.g., the diorganosiloxane compound) may be from 1to 39 wt %, alternatively from 3 to 30 wt %, alternatively from 4 to 20wt % of the curable silicone composition. Alternatively, the ingredient(A) may be from 50 to 90 wt %, alternatively from 60 to 80 wt %,alternatively from 70 to 80 wt % of the hydrosilylation-curableorganosiloxane.

Ingredient (B), the organohydrogensilicon compound, has at least onesilicon-bonded hydrogen atom per molecule. The organohydrogensiliconcompound may be a single organohydrogensilicon compound, or a pluralityof different organohydrogensilicon compounds. The organohydrogensiliconcompound may have organo groups and an average of at least two,alternatively at least three silicon-bonded hydrogen atoms per molecule.Each organo group independently may be the same as R, R¹, or R⁴ groupsas defined before. The organohydrogensilicon compound may be anorganohydrogensilane, an organohydrogensiloxane, or a combinationthereof. The structure of the organohydrogensilicon compound may belinear, branched, cyclic (e.g., Cyclosilanes and cyclosiloxanes), orresinous. Cyclosilanes and cyclosiloxanes may have from 3 to 12,alternatively from 3 to 10, alternatively 3 or 4 silicon atoms. Inacyclic polysilanes and polysiloxanes, the silicon-bonded hydrogen atomsmay be located at terminal, pendant, or at both terminal and pendantpositions.

Referring to an embodiment of ingredient (B), the organohydrogensilanemay be a monosilane, disilane, trisilane, or polysilane (tetra- orhigher silane). Examples of suitable organohydrogensilanes arediphenylsilane, 2-chloroethylsilane, bis[(p-dimethylsilyl)phenyl]ether,1,4-dimethyldisilylethane, 1,3,5-tris(dimethylsilyl)benzene,1,3,5-trimethyl-1,3,5-trisilane, poly(methylsilylene)phenylene, andpoly(methylsilylene)methylene.

Referring to an embodiment of ingredient (B), the organohydrogensiloxanemay be a disiloxane, trisiloxane, or polysiloxane (tetra- or highersiloxane). The organohydrogensiloxane may be further defined as anorganohydrogenpolysiloxane resin, so long as the resin includes at leastone silicon-bonded hydrogen atom per molecule. Theorganohydrogenpolysiloxane resin may be a copolymer including T units,and/or Q units, in combination with M units, and/or D units, wherein T,Q, M and D are as described above. For example, theorganohydrogenpolysiloxane resin can be a DT resin, an MT resin, an MDTresin, a DTQ resin, an MTQ resin, an MDTQ resin, a DQ resin, an MQresin, a DTQ resin, an MTQ resin, or an MDQ resin. The M, D, T and Qunits may be the same as those described previously. Examples ofsuitable organohydrogensiloxanes are 1,1,3,3-tetramethyldisiloxane,1,1,3,3-tetraphenyldisiloxane, phenyltris(dimethylsiloxy)silane,1,3,5-trimethylcyclotrisiloxane, a trimethylsiloxy-terminatedpoly(methylhydrogensiloxane), a trimethylsiloxy-terminatedpoly(dimethylsiloxane/methylhydrogensiloxane), adimethylhydrogensiloxy-terminated poly(methylhydrogensiloxane), and a(H,Me)Si resin. Thus, the organohydrogensilicon compound may be thetrimethylsiloxy-terminatedpoly(dimethylsiloxane/methylhydrogensiloxane).

Referring again to ingredient (B), the organohydrogensilicon compoundmay have a molecular weight less than 1,000, alternatively less than750, alternatively less than 500 g/mol. The organohydrogensiliconcompound may be a dimethylhydrogensilyl terminated polydimethylsiloxane;alternatively a trialkylsilyl terminatedpolydialkylsiloxane-alkylhydrogensiloxane co-polymer; alternatively atrimethylsilyl terminated polydimethylsiloxane-methylhydrogensiloxane copolymer; alternatively a mixture of a dialkylhydrogensilyl terminatedpolydialkylsiloxane and a trialkylsilyl terminatedpolydialkylsiloxane-alkylhydrogensiloxane co-polymer. Thedialkylhydrogensilyl terminated polydialkylsiloxane may be adimethylhydrogensilyl terminated polydimethylsiloxane. The trialkylsilylterminated polydialkylsiloxane-alkylhydrogensiloxane co-polymer may be atrimethylsilyl terminated polydimethylsiloxane-methylhydrogensiloxaneco-polymer.

The ingredient (B) (e.g., the organohydrogensilicon compound) may befrom 0.1 to 10 wt %, alternatively from 0.2 to 8 wt %, alternativelyfrom 0.3 to 5 wt % of the curable silicone composition. Alternatively,the ingredient (B) may be from 1 to 10 wt %, alternatively from 2 to 8wt %, alternatively from 3 to 7 wt % of the hydrosilylation-curableorganosiloxane.

Referring again to ingredients (A) and (B), the hydrosilylation-curableorganosiloxane may have a molar ratio of total silicon-bonded hydrogenatoms to unsaturated carbon-carbon bonds of from 0.05 to 100,alternatively from 0.1 to 100, alternatively from 0.05 to 20,alternatively from 0.5 to 15, alternatively from 1.5 to 14. Wheningredients (A) and (B) are different molecules, thehydrosilylation-curable organosiloxane may have a molar ratio ofsilicon-bonded hydrogen atoms per molecule of the organohydrogensiliconcompound to unsaturated carbon-carbon bonds per molecule of thediorganosiloxane compound of from 0.05 to 100, alternatively from 0.1 to100, alternatively from 0.05 to 20, alternatively from 0.5 to 14,alternatively from 0.5 to 2, alternatively from 1.5 to 5, alternativelyfrom >5 to 14. The present invention, however, is not limited to thehydrosilylation-curable organosiloxane comprising ingredients (A) and(B).

Ingredient (C), the hydrosilylation catalyst, is any compound ormaterial useful to accelerate a hydrosilylation reaction between thediorganosiloxane compound and the organohydrogensilicon compound. Thehydrosilylation catalyst may comprise a metal; a compound containing themetal; or any combination thereof. Each metal independently be platinum,rhodium, ruthenium, palladium, osmium, or iridium, or any combination ofat least two thereof. Typically, the metal is platinum, based on itshigh activity in hydrosilylation reactions. Typically ingredient (C) isthe platinum compound. Examples of suitable platinum hydrosilylationcatalysts are complexes of chloroplatinic acid and certainvinyl-containing organosiloxanes in U.S. Pat. No. 3,419,593 such as thereaction product of chloroplatinic acid andI,3-diethenyl-I,I,3,3-tetramethyldisiloxane. The hydrosilylationcatalyst may be unsupported or disposed on a solid support (e.g.,carbon, silica, or alumina). The hydrosilylation catalyst may bemicroencapsulated in a thermoplastic resin for increased stabilityduring storage of the curable silicone composition comprising thehydrosilylation-curable organosiloxane before curing. When curing isdesired, the microencapsulated catalyst (e.g., see U.S. Pat. No.4,766,176 and U.S. Pat. No. 5,017,654) may be heated about the meltingor softening point of the thermoplastic resin, thereby exposing thehydrosilylation catalyst to ingredients (A) and (B). The hydrosilylationcatalyst may be a photoactivatable catalyst (e.g., platinum(II)β-diketonate complexes such as platinum(II) bis(2,4-pentanedionate)) forincreased stability during storage of the curable silicone compositionbefore curing. When curing is desired, the photoactivatable catalyst maybe exposed to ultraviolet radiation having a wavelength of from 150 to800 nanometers (nm), thereby activating the catalyst to thehydrosilylation reaction of ingredients (A) and (B).

Ingredient (C) typically is employed in a catalytically effectiveamount. The catalytically effective amount of the hydrosilylationcatalyst is any quantity sufficient to catalyze, increase the rate ofhydrosilylation of the diorganosiloxane compound andorganohydrogensilicon compound. A suitable concentration of theunsupported and unencapsulated hydrosilylation catalyst in thehydrosilylation-curable organosiloxane is from 0.1 to 1000 parts permillion (ppm), alternatively from 1 to 500 ppm, alternatively from 3 to150 ppm, alternatively from 1 to 25 ppm, based on the combined weight ofingredients (A) to (C). A suitable concentration of themicroencapsulated hydrosilylation catalyst in thehydrosilylation-curable organosiloxane is from 1 to 20 wt %,alternatively from 3 to 17 wt %, alternatively from 5 to 15 wt %,alternatively from 10 to 15 wt %, all based on the combined weight ofingredients (A) to (C).

The curable organosiloxane composition (e.g., ingredients (A) to (C))may be from 7 to 25 wt %, alternatively from 7.0 to 20 wt %,alternatively from 8 to 16 wt %, all based on the weight of the curablesilicone composition.

Optional ingredients. As described earlier, the curable siliconecomposition comprises the following original ingredients: thehydrocarbon vehicle, curable organosiloxane composition, and the Cu—Agcore-shell particles. In some embodiments the curable siliconecomposition and ECSA lack additional ingredients. The term “lack” meanscontains less than the minimum concentration of; alternatively iscompletely free of, does not contain (e.g., contains 0.000 wt % of), ordoes not include any. However, whether curable by hydrosilylation,condensation, free radical, or other chemistry, it may be desirable forthe curable silicone composition and ECSA to further comprise at leastone additional ingredient that is distinct from the originalingredients. The at least one additional ingredient should not affectthe basic and novel characteristics of the present invention, e.g.,achieving one or more of the advantages described herein for the curablesilicone composition and ECSA.

In some embodiments the curable silicone composition and ECSA furthercomprise the at least one additional ingredient. The amount of the atleast one additional ingredient, when present in the curable siliconecomposition, or the curable silicone composition and ECSA preparedtherefrom, is not so high as to prevent the curable silicone compositionfrom satisfying at least the minimum concentrations of the originalingredients or prevent the ECSA from satisfying its limitations such asvolume resistivity, total silver concentration, and other functions andconcentrations as described herein. When present in the curable siliconecomposition, the at least one additional ingredient may be at a totalconcentration of 0.01 to 5 wt % based on total weight of the curablesilicone composition. When present, the total concentration of all theadditional ingredients is from 0.1 to 2 wt %, alternatively from 0.1 to1 wt %.

The curable silicone composition may be prepared with the at least oneadditional ingredient in any suitable manner. For example, the at leastone additional ingredient may be premixed with the curableorganosiloxane composition or a diorganosiloxane ingredient thereof. Theresulting premixture may then be blended with the hydrocarbon vehicle,any other ingredients of the curable organosiloxane composition, andelectrically conductive filler to prepare embodiments of the curablesilicone composition wherein the blend further comprises the at leastone additional ingredient.

Typically, the at least one additional ingredient includes the MTF,alternatively an adhesion promoter, more typically an organosiloxaneadhesion promoter, alternatively the carbon nanotubes and theorganosiloxane adhesion promoter. Alternatively or additionally, the atleast one additional ingredient may be one or more of a siliconeextender, organic plasticizer, or a combination of silicone extender andorganic plasticizer; a curing inhibitor (e.g., a hydrosilylationreaction inhibitor when the curable silicone composition is ahydrosilylation curable silicone composition); a defoamer; a biocide; achain lengthener; a chain endblocker; an anti-aging additive; an acidacceptor; and a combination of any two or more selected from theimmediately foregoing listing (i.e., the listing from the siliconeextender to the acid acceptor). Alternatively, the at least oneadditional ingredient may be a combination of the adhesion promoter andany one or more selected from the immediately foregoing listing from thesilicone extender to the acid acceptor. For example, the adhesionpromoter may be used in combination with the silicone extender,hydrosilylation reaction inhibitor, or both. The at least one additionalingredient may be the adhesion promoter, alternatively the siliconeextender, alternatively the organic plasticizer, alternatively thecombination of silicone extender and organic plasticizer, alternativelythe curing inhibitor, alternatively the defoamer, alternatively thebiocide, alternatively the chain lengthener, alternatively the chainendblocker, alternatively the anti-aging additive, alternatively theacid acceptor, alternatively any one of the combinations. Additionally,it is convenient to name optional ingredients by an intended use of theoptional ingredient in the curable silicone composition and/or ECSA. Theintended use, however is not limiting of the chemistry of the so-namedoptional ingredient and does not restrict how the so-named optionalingredient may react or function during curing of the curable siliconecomposition to give the ECSA. To illustrate, a so-called adhesionpromoter may function in the curable silicone composition and/or ECSA asan adhesion promoter and optionally as a chain lengthener, crosslinker,silicone extender, or any combination of adhesion promoter and one ormore of chain lengthener, crosslinker and silicone extender. Theingredients of the curable silicone composition and ECSA may bechemically compatible with the Cu—Ag core-shell particles such thatoxidation of the Cu(0) cores is inhibited or prevented.

The adhesion promoters useful in the present invention may comprise ametal chelate, a silicon-based adhesion promoter, or a combination ofany two or more thereof. The combination may be a combination of themetal chelate and at least one silicon-based adhesion promoter or acombination of at least two different silicon-based adhesion promoters.The different silicon-based adhesion promoters differ from each other inat least one of the following properties: structure, viscosity, averagemolecular weight, siloxane units, and unit sequence. Further, thesilicon-based adhesion promoters differ from other silicon-basedingredients of the curable organosiloxane composition (e.g., ingredients(A) and (B) of the embodiment(s) of the hydrosilylation-curableorganosiloxane) in at least one of the following properties: structure,viscosity, average molecular weight, siloxane units, and unit sequence.In some embodiments the curable silicone composition and ECSA lack theadhesion promoter; in other embodiments they further comprise theadhesion promoter.

The metal chelate adhesion promoter may be based on a metal that islead, tin, zirconium, antimony, zinc, chromium, cobalt, nickel,aluminum, gallium, germanium, or titanium. The metal chelate maycomprise the metal cation and an anionic chelating ligand such as amonocarboxylate, dicarboxylate, or alkoxide. The adhesion promoter maycomprise a non-transition metal chelate such as an aluminum chelate suchas aluminum acetylacetonate. Alternatively, the metal chelate may be atransition metal chelate. Suitable transition metal chelates includetitanates, zirconates such as zirconium acetylacetonate, andcombinations thereof. The metal chelate may be the titanium chelate.Alternatively, the adhesion promoter may comprise a combination of ametal chelate with an alkoxysilane, such as a combination ofglycidoxypropyltrimethoxysilane with an aluminum chelate or a zirconiumchelate. Alternatively, the metal chelate may lack silicon. Example ofsuitable metal chelates are mentioned in U.S. Pat. No. 4,680,364 atcolumn 3, line 65, to column 6, line 59.

Typically, the adhesion promoter is the silicon-based adhesion promoter.Suitable silicon-based adhesion promoters include ahydrocarbyloxysilane, a combination of an alkoxysilane and ahydroxy-functional polyorganosiloxane, an aminofunctional silane, or acombination of any two or more thereof. The hydrocarbyloxysilane may bean alkoxysilane.

For example, the adhesion promoter may comprise a silane having theformula R¹⁹ _(r)R²⁰ _(s)Si(OR²¹)_(4-(r+s)) where each R¹⁹ isindependently a monovalent organic group having at least 3 carbon atoms;R²⁰ contains at least one Si—C-substituent wherein the substituent hasan adhesion-promoting group, such as amino, epoxy, mercapto or acrylategroups; each R²¹ is independently a saturated hydrocarbon group;subscript r has a value ranging from 0 to 2; subscript s is either 1 or2; and the sum of (r+s) is not greater than 3. Saturated hydrocarbongroups for R²¹ may be an alkyl group of 1 to 4 carbon atoms,alternatively alkyl of 1 or 2 carbon atoms. R²¹ may be methyl, ethyl,propyl, or butyl; alternatively R²¹ may be methyl. Alternatively, theadhesion promoter may comprise a partial condensate of the above silane.Alternatively, the adhesion promoter may comprise a combination of analkoxysilane and a hydroxy-functional polyorganosiloxane.

Alternatively, the adhesion promoter may comprise an unsaturated orepoxy-functional compound. The adhesion promoter may comprise anunsaturated or epoxy-functional alkoxysilane. For example, thefunctional alkoxysilane can have the formula R²² _(t)Si(OR²³)_((4-t)),where subscript t is 1, 2, or 3, alternatively subscript t is 1. EachR²² is independently a monovalent organic group with the proviso that atleast one R²² is an unsaturated organic group or an epoxy-functionalorganic group. Epoxy-functional organic groups for R²² are exemplifiedby 3-glycidoxypropyl and (epoxycyclohexyl)ethyl. Unsaturated organicgroups for R²² are exemplified by 3-methacryloyloxypropyl,3-acryloyloxypropyl, and unsaturated monovalent hydrocarbon groups suchas vinyl, allyl, hexenyl, undecylenyl. Each R²³ is independently asaturated hydrocarbon group of 1 to 4 carbon atoms, alternatively 1 to 2carbon atoms. R²³ is exemplified by methyl, ethyl, propyl, and butyl.

Examples of suitable epoxy-functional alkoxysilane type adhesionpromoters include 3-glycidoxypropyltrimethoxysilane,3-glycidoxypropyltriethoxysilane, (epoxycyclohexyl)ethyldimethoxysilane,(epoxycyclohexyl)ethyldiethoxysilane and combinations thereof. Examplesof suitable unsaturated alkoxysilanes include vinyltrimethoxysilane,allyltrimethoxysilane, allyltriethoxysilane, hexenyltrimethoxysilane,undecylenyltrimethoxysilane, 3-methacryloyloxypropyl trimethoxysilane,3-methacryloyloxypropyl triethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-acryloyloxypropyl triethoxysilane, and combinationsthereof.

Alternatively, the adhesion promoter may comprise an epoxy-functionalorganosiloxane such as a reaction product of a hydroxy-terminatedpolyorganosiloxane with an epoxy-functional alkoxysilane, as describedabove, or a physical blend of the hydroxy-terminated polyorganosiloxanewith the epoxy-functional alkoxysilane. The epoxy-functionalorganosiloxane comprises one or more, alternatively two or more epoxygroups and at least one type of organogroup such as the alkyl, alkenyl,alkynyl, aryl, or organoheteryl. The epoxy group(s) independently may becovalently bonded directly to a silicon atom of the organosiloxanylportion of the epoxy-functional organosiloxane or to any carbon atom ofthe organogroup. The epoxy group(s) may be located at internal,terminal, or both positions of the organosiloxanyl portion. Theepoxy-functional organosiloxane may be an epoxy-functionaldiorganosiloxane, an epoxy-functional organo, hydrogensiloxane; or anepoxy-functional diorgano/(organo,hydrogen)siloxane. The“diorgano/(organo,hydrogen)” indicates the siloxane has both diorganoSiD units (“D”) and organo-SiH D units (D^(H)) in the organosiloxanylportion. The organogroups in any one of such diorganoSi D units may bethe same as or different from each other. For example, theepoxy-functional diorganosiloxane may be abis(alpha,omega-glycidoxyalkyl)dialkyl/(alkyl,alkenyl)siloxane. The“dialkyl/(alkyl,alkenyl)” indicates siloxane has both dialkylSi D unitsand alkyl,alkenylSi D units. The “bis(alpha,omega-glycidoxyalkyl)”indicates a dialkyl/alkyl,alkenylsiloxanyl moiety has two terminalglycidoxyalkyl groups, and 0 or optionally 1 or more internalglycidoxyalkyl groups. Alternatively, the adhesion promoter may comprisea combination of an epoxy-functional alkoxysilane and anepoxy-functional siloxane. For example, the adhesion promoter isexemplified by a mixture of 3-glycidoxypropyltrimethoxysilane and areaction product of hydroxy-terminated methylvinylsiloxane (i.e.,hydroxy-terminated poly(methyl,vinyl)siloxane) with3-glycidoxypropyltrimethoxysilane, or a mixture of3-glycidoxypropyltrimethoxysilane and a hydroxy-terminatedmethylvinylsiloxane, or a mixture of 3-glycidoxypropyltrimethoxysilaneand a hydroxy-terminated methylvinyl/dimethylsiloxane copolymer.

Alternatively, the adhesion promoter may comprise an epoxy-functionalorganocyclosiloxane. The epoxy-functional organocyclosiloxane comprisesone or more, alternatively two or more epoxy groups and at least onetype of organogroup such as the alkyl, alkenyl, alkynyl, aryl, ororganoheteryl. For example, the epoxy-functional organocyclosiloxane maybe an epoxy-functional D3 to D6 diorganocyclosiloxane; anepoxy-functional D3 to D6 organo,hydrogencyclosiloxane; or anepoxy-functional D3 to D6 diorgano/(organo,hydrogen)cyclosiloxane. TheD3 is an organocyclotrisiloxane; D4 is an organocyclotetrasiloxane; D5is an organocyclopentasiloxane; and D6 is an organocyclohexasiloxane.The epoxy-functional organocyclosiloxane may have one or more,alternatively two or more organocyclosiloxanyl moieties, wherein any twoorganocyclosiloxanyl moieties may be linked to each other via analkylene-diorganosiloxanylene-alkylene chain. For example, theepoxy-functional D3 to D6 organo,hydrogencyclosiloxane may be abis(alpha,omega-glycidoxyalkyl-D3 to D6 organo,hydrogencyclosiloxane),wherein there are at least two glycidoxyalkyl moieties; there are atleast two organo,hydrogencyclosiloxanyl moieties, which may be the sameas or different from each other; and any twoorgano,hydrogencyclosiloxanyl moieties independently are linked to eachother via an alkylene-diorganosiloxanylene-alkylene chain. The alkyl maybe methyl and the alkenyl may be vinyl. Each chain may be the same as ordifferent from each other, may be linear or branched, and may have abackbone of from 3 to 100, alternatively from 5 to 90, alternativelyfrom 8 to 50 atoms, wherein the backbone atoms are C, Si, and O. Theepoxy group(s) independently may be covalently bonded directly to asilicon atom of the organocyclosiloxanyl moiety or, when there are twoor more organocyclosiloxanyl moieties, to a silicon atom of thealkylene-diorganosiloxanylene-alkylene chain; or the epoxy group(s) maybe covalently bonded directly to any carbon atom of any organogroupthereof. The groups in any D unit may be the same as or different fromeach other.

Alternatively, the adhesion promoter may comprise an aminofunctionalsilane, such as an aminofunctional alkoxysilane exemplified byH₂N(CH₂)₂Si(OCH₃)₃, H₂N(CH₂)₂Si(OCH₂CH₃)₃, H₂N(CH₂)₃Si(OCH₃)₃,H₂N(CH₂)₃Si(OCH₂CH₃)₃, CH₃NH(CH₂)₃Si(OCH₃)₃, CH₃NH(CH₂)₃Si(OCH₂CH₃)₃,CH₃NH(CH₂)₅Si(OCH₃)₃, CH₃NH(CH₂)₅Si(OCH₂CH₃)₃,H₂N(CH₂)₂NH(CH₂)₃Si(OCH₃)₃, H₂N(CH₂)₂NH(CH₂)₃Si(OCH₂CH₃)₃,CH₃NH(CH₂)₂NH(CH₂)₃SROCH₃)₃, CH₃NH(CH₂)₂NH(CH₂)₃Si(OCH₂CH₃)₃,C₄H₉NH(CH₂)₂NH(CH₂)₃Si(OCH₃)₃, C₄H₉NH(CH₂)₂NH(CH₂)₃Si(OCH₂CH₃)₃,H₂N(CH₂)₂SiCH₃(OCH₃)₂, H₂N(CH₂)₂SiCH₃(OCH₂CH₃)₂, H₂N(CH₂)₃SiCH₃(OCH₃)₂,H₂N(CH₂)₃SiCH₃(OCH₂CH₃)₂, CH₃NH(CH₂)₃SiCH₃(OCH₃)₂,CH₃NH(CH₂)₃SiCH₃(OCH₂CH₃)₂, CH₃NH(CH₂)₅SiCH₃(OCH₃)₂,CH₃NH(CH₂)₅SiCH₃(OCH₂CH₃)₂, H₂N(CH₂)₂NH(CH₂)₃SiCH₃(OCH₃)₂,H₂N(CH₂)₂NH(CH₂)₃SiCH₃(OCH₂CH₃)₂, CH₃NH(CH₂)₂NH(CH₂)₃SiCH₃(OCH₃)₂,CH₃NH(CH₂)₂NH(CH₂)₃SiCH₃(OCH₂CH₃)₂, C₄H₉NH(CH₂)₂NH(CH₂)₃SiCH₃(OCH₃)₂,C₄H₉NH(CH₂)₂NH(CH₂)₃SiCH₃(OCH₂CH₃)₂, and a combination thereof.

The concentration of adhesion promoter, when present, may be from 0.1 to5 wt %, alternatively from 0.1 to 7 wt %, alternatively from 0.1 to 5 wt%, alternatively from 0.1 to 2 wt %, alternatively from 0.2 to 1.0 wtall based on weight of the curable silicone composition.

The silicone extender may be an unsubstituted hydrocarbyl-containing MDorganosiloxane such as a bis(trihydrocarbyl-terminated)dihydrocarbylorganosiloxane, wherein each hydrocarbyl independently isunsubstituted (C₁-C₁₀)alkyl (e.g., methyl), (C₂-C₁₀)alkenyl,(C₂-C₁₀)alkynyl, benzyl, phenethyl, phenyl, tolyl, or naphthyl. Examplesof the silicone extender are polydimethylsiloxanes, including DOWCORNING® 200 Fluids, Dow Corning Corporation, Midland, Mich., USA. Thesefluids may have kinematic viscosity ranging from 50 to 100,000centiStokes (cSt; 50 to 100,000 square millimeters per second (mm²/s)),alternatively 50 to 50,000 cSt (50 to 50,000 mm²/s), and alternatively12,500 to 60,000 cSt (12,500 to 60,000 mm²/s). The kinematic viscosityis measured according to the method described later. In some embodimentsthe curable silicone composition and ECSA lack the silicone extender; inother embodiments they further comprise the silicone extender. Theconcentration of the silicone extender, when present, may be from 0.1 to10 wt %, alternatively from 0.5 to 5 wt %, alternatively from 1 to 5 wt%, all based on weight of the curable silicone composition.

The curing inhibitor may be the hydrosilylation reaction inhibitor whenthe curable silicone composition is a hydrosilylation curable siliconecomposition. The hydrosilylation reaction inhibitor may be used to delayonset of, inhibit, slow the reaction rate of, or prevent start of thehydrosilylation reaction of the hydrosilylation-curable organosiloxaneas compared to that of the same composition but with the hydrosilylationreaction inhibitor omitted therefrom. Examples of suitablehydrosilylation reaction inhibitors are acetylenic alcohols, silylatedacetylenic compounds, cycloalkenylsiloxanes, ene-yne compounds,phosphines, mercaptans, hydrazines, amines, fumarate diesters, andmaleate diesters, Examples of the acetylenic alcohols are 1-propyn-3-ol;1-butyn-3-ol; 2-methyl-3-butyn-2-ol; 3-methyl-1-butyn-3-ol;3-methyl-1-pentyn-3-ol; 4-ethyl-1-octyn-3-ol; 1-ethynyl-1-cyclohexanol;3,5-dim ethyl-1-hexyn-3-ol; 4-ethyl-1-octyn-3-ol;1-ethynyl-1-cyclohexanol; 3-phenyl-1-butyn-3-ol; and2-phenyl-3-butyn-2-ol. E.g., the hydrosilylation reaction inhibitor maybe 1-ethynyl-1-cyclohexanol. Examples of cycloalkenylsiloxanes aremethylvinylcyclosiloxanes, e.g.,1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane and1,3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane. Examples ofene-yne compounds are 3-methyl-3-penten-I-yne and3,5-dimethyl-3-hexen-I-yne. An example of phosphines istriphenylphosphine. Examples of fumarate diesters are dialkyl fumarates,dialkenyl fumarates (e.g., diallyl fumarates), and dialkoxyalkylfumarates. Examples of maleate diesters are dialklyl maleates anddiallyl maleates. Examples of silylated acetylenic compounds are(3-methyl-1-butyn-3-oxy)trimethylsilane,((1,1-dimethyl-2-propynyl)oxy)trimethylsilane,bis(3-methyl-1-butyn-3-oxy)dimethylsilane,bis(3-methyl-1-butyn-3-oxy)silanemethylvinylsilane,bis((1,1-dimethyl-2-propynyloxy)dimethylsilane,methyl(tris(1,1-dimethyl-2-propynyloxy))silane,methyl(tris(3-methyl-1-butyn-3-oxy))silane,(3-methyl-1-butyn-3-oxy)dimethylphenylsilane,(3-methyl-1-butyn-3-oxy)dimethylhexenylsilane,(3-methyl-1-butyn-3-oxy)triethylsilane,bis(3-methyl-1-butyn-3-oxy)methyltrifluoropropylsilane,(3,5-dimethyl-1-hexyn-3-oxy)trimethylsilane,(3-phenyl-1-butyn-3-oxy)diphenylmethylsilane,(3-phenyl-1-butyn-3-oxy)dimethylphenylsilane,(3-phenyl-1-butyn-3-oxy)dimethylvinylsilane,(3-phenyl-1-butyn-3-oxy)dimethylhexenylsilane,(cyclohexyl-1-ethyn-1-oxy)dimethylhexenylsilane,(cyclohexyl-1-ethyn-1-oxy)dimethylvinylsilane,(cyclohexyl-1-ethyn-1-oxy)diphenylmethylsilane, and(cyclohexyl-1-ethyn-1-oxy)trimethylsilane. The hydrosilylation reactioninhibitor may be methyl(tris(1,1-dimethyl-2-propynyloxy))silane or((1,1-dimethyl-2-propynyl)oxy)trimethylsilane. The hydrosilylationreaction inhibitor may be a combination of any two or more of theforegoing examples, either taken from within a single structural classor from at least two different structural classes. In some embodimentsthe curable silicone composition and ECSA lack the hydrosilylationreaction inhibitor; in other embodiments they further comprise thehydrosilylation reaction inhibitor. The concentration of thehydrosilylation reaction inhibitor, when present, may be from 0.1 to 5wt %, alternatively from 0.5 to 2 wt %, all based on weight of thecurable silicone composition.

The defoamer may be used to inhibit or prevent foaming during formationof the curable silicone composition or the curable organosiloxanecomposition. In some embodiments the curable silicone composition andECSA lack the defoamer; in other embodiments they further comprise thedefoamer.

The biocide may be an antimicrobial compound, antibacterial compound,antiviral compound, fungicide, herbicide, or pesticide. The biocide maybe used to inhibit contamination or degradation of the curable siliconecomposition or the curable organosiloxane composition duringmanufacturing, storage, transportation, or application thereof; and/orinhibit contamination or degradation of the ECSA during curing and oruse in the electrical component. In some embodiments the curablesilicone composition and ECSA lack the biocide; in other embodimentsthey further comprise the biocide.

The chain lengthener may be used to extend lengths of chains ofingredients (A), (B), or (A) and (B) before any coupling or crosslinkingoccurs during curing of the curable silicone composition. Examples ofsuitable chain lengtheners are difunctional silanes (e.g.,1,1,2,2-tetramethyldisilane) and difunctional siloxanes (e.g., adimethylhydrogen-terminated terminated polydimethylsiloxane having adegree of polymerization (DP) of from 3 to 50, e.g., from 3 to 10). Insome embodiments the curable silicone composition and ECSA lack thechain lengthener; in other embodiments they further comprise the chainlengthener. The concentration of the chain lengthener, when present, maybe from 0.1 to 10 wt %, alternatively from 0.5 to 5 wt %, all based onweight of the curable silicone composition.

The chain endblocker may be used to terminate a chain and preventfurther extending or crosslinking during curing of the curable siliconecomposition. The chain endblocker may be an unsubstitutedhydrocarbyl-containing siloxane M unit, wherein the hydrocarbylindependently is as described for the hydrocarbyl of the siliconeextender. An example of a suitable chain endblocker is an organosiloxanehaving one or more trimethylsiloxy groups. In some embodiments thecurable silicone composition and ECSA lack the chain endblocker; inother embodiments they further comprise the chain endblocker. Theconcentration of the chain endblocker, when present, may be from 0.1 to10 wt %, alternatively from 0.5 to 5 wt %, all based on weight of thecurable silicone composition.

The anti-aging additive may be used to delay onset of, inhibit, decreaserate of, or prevent degradation of the curable silicone compositionand/or ECSA when exposed to degradation-promoting condition(s). Examplesof degradation promoting conditions are exposure to oxidant, ultravioletlight, heat, moisture, or a combination of any two or more thereof.Examples of suitable anti-aging additives are antioxidants, UVabsorbers, UV stabilizers, heat stabilizers, desiccants, andcombinations thereof. Suitable antioxidants include sterically hinderedphenols (e.g., vitamin E). Suitable UV absorbers/stabilizers includephenol. Suitable heat stabilizers include iron oxides and carbon blacks.Suitable moisture stabilizers include anhydrous forms of silica,magnesium oxide and calcium oxide. In some embodiments the curablesilicone composition and ECSA lack the anti-aging additive; in otherembodiments they further comprise the anti-aging additive. Theconcentration of the anti-aging additive, when present, may be from 0.01to 5 wt %, alternatively from 0.1 to 2 wt %, all based on weight of thecurable silicone composition.

In some embodiments the curable silicone composition is a curablesilicone composition comprising a blend of the following ingredients: anisoalkanes mixture comprising at least three of (C₁₂-C₁₆)isoalkanes andhas an initial boiling point of greater than 210 degrees Celsius and anend boiling point of less than 270 degrees Celsius and the hydrocarbonvehicle is at a concentration of from 4.5 to 12 wt % based on weight ofthe curable silicone composition; a hydrosilylation-curablepolydimethylsiloxane composition comprising at least onevinyl-functional polydimethylsiloxane compound having on average permolecule at least 1 vinyl moieties, at least onetrimethylsiloxy-terminated dimethyl methylhydrogensilicon compoundhaving on average per molecule at least 1.1 Si—H moieties, amicroencapsulated platinum hydrosilylation catalyst, andbis(alpha,omega-glycidoxyalkyl)-dialkyl/(alkyl,alkenyl)siloxane, andbis(alpha,omega-glycidoxyalkyl-D3 to D6 alkyl,hydrogencyclosiloxane; andwherein the vinyl-functional polydimethylsiloxane compound is from 70 to75 wt %, the trimethylsiloxy-terminated dimethyl methylhydrogensiliconcompound is from 1 to 5 wt %, the microencapsulated hydrosilylationcatalyst is from 10 to 15 wt %, thebis(alpha,omega-glycidoxyalkyl)-dialkyl/(alkyl,alkenyl)siloxane is from1 to 10 wt %, and the bis(alpha,omega-glycidoxyalkyl-D3 to D6alkyl,hydrogencyclosiloxane is from 0 to 7 wt %, all of the curablepolydimethylsiloxane composition; and wherein together thetrimethylsiloxy-terminated dimethyl methylhydrogensilicon compound,microencapsulated hydrosilylation catalyst, and thebis(alpha,omega-glycidoxyalkyl)-dialkyl/(alkyl,alkenyl)siloxane, andbis(alpha,omega-glycidoxyalkyl-D3 to D6 alkyl,hydrogencyclosiloxane arefrom 20 to 30 wt % of the curable organosiloxane composition; Cu—Agcore-shell particles are at a concentration of from 79.9 to 86.0 wt %based on weight of the curable silicone composition; wherein the totalconcentration of silver is from 7.5 to 12 wt % based on weight of thecurable silicone composition; and carbon nanotubes at a concentration offrom 0.50 to 1.5 wt % based on weight of the curable siliconecomposition; and wherein the curable silicone composition ischaracterizable by a volume resistivity less than 0.00090 Ohm-centimetermeasured according to Volume Resistivity Test Method.

Alternatively, the vinyl-functional polydimethylsiloxane compound may befrom 70 to 75 wt % of the hydrosilylation-curable polydimethylsiloxanecomposition; the trimethylsiloxy-terminated dimethylmethylhydrogensilicon compound may be from 1 to 5 wt % of thehydrosilylation-curable polydimethylsiloxane composition; themicroencapsulated hydrosilylation catalyst may be from 10 to 15 wt % ofthe hydrosilylation-curable polydimethylsiloxane composition; thebis(alpha,omega-glycidoxyalkyl-D3 to D6 alkyl,hydrogencyclosiloxane) maybe from 0 to 7 wt % (e.g., 0 wt %), alternatively from 0.1 to 7 wt % ofthe hydrosilylation-curable polydimethylsiloxane composition, and thebis(alpha,omega-glycidoxyalkyl)-dialkyl/(alkyl,alkenyl)siloxane adhesionpromoter may be from 0.1 to 10 wt %, alternatively from 1 to 10 wt %, ofthe hydrosilylation-curable polydimethylsiloxane composition. Prior toits use to prepare the curable silicone composition, thehydrosilylation-curable polydimethylsiloxane composition may lack thehydrocarbon vehicle, Cu—Ag core-shell particles, and MTF, if any. As forconcentrations of the ingredients in terms of wt % of the curablesilicone composition prepared with the hydrosilylation-curablepolydimethylsiloxane composition, the vinyl-functionalpolydimethylsiloxane compound may be from 16 to 18 wt % (e.g., 17 wt %)of the curable silicone composition, the trimethylsiloxy-terminateddimethyl methylhydrogensilicon compound may be from 0.1 to 2 wt % (e.g.,1 wt %) of the curable silicone composition, the microencapsulatedhydrosilylation catalyst may be from 2 to 5 wt % (e.g., 3 wt %) of thecurable silicone composition, and thebis(alpha,omega-glycidoxyalkyl)-dialkyl/(alkyl,alkenyl)siloxane adhesionpromoter may be from 1 to 4 wt % (e.g., 2 wt %) of the curable siliconecomposition. In such an embodiment of the curable silicone compositionthe concentration of the hydrocarbon vehicle may be from 4.9 to 12 wt %of the curable silicone composition, the Cu—Ag core-shell particles maybe Cu—Ag core-shell flakes, alternatively Cu—Ag core-shell spheres, andthe MTF, if any, may be multi-walled carbon nanotubes, wherein themulti-walled carbon nanotubes are at a concentration of from 0.50 to0.94 wt %, all of the curable silicone composition. In such anembodiment, the total concentration of Cu—Ag core-shell may be from 79.5to 86 wt % of the curable silicone composition. When the curablesilicone composition also contains the bis(alpha,omega-glycidoxyalkyl-D3to D6 alkyl,hydrogencyclosiloxane), the concentration of thebis(alpha,omega-glycidoxyalkyl-D3 to D6 alkyl,hydrogencyclosiloxane) maybe from 0.5 to 1.5 wt % (e.g., 1 wt %) of the curable siliconecomposition.

The concentration of SiH-containing ingredients may be adjusted in thecurable silicone composition such that the total SiH concentration inthe curable silicone composition may be reached with differentproportions of the SiH-containing ingredients. For example, when thecurable silicone composition also contains thebis(alpha,omega-glycidoxyalkyl-D3 to D6 alkyl,hydrogencyclosiloxane),the concentration of the trimethylsiloxy-terminated dimethylmethylhydrogensilicon compound may be from 0.2 to 0.9 wt % (e.g., 0.5 wt%) and the concentration of the bis(alpha,omega-glycidoxyalkyl-D3 to D6alkyl,hydrogencyclosiloxane) may be from 0.5 to 1.5 wt % (e.g., 1 wt %),both based on weight of the curable silicone composition. When thecurable silicone composition lacks (i.e., 0 wt %) thebis(alpha,omega-glycidoxyalkyl-D3 to D6 alkyl,hydrogencyclosiloxane),the concentration of the trimethylsiloxy-terminated dim ethylmethylhydrogensilicon compound may be from 0.2 to 1.5, alternativelyfrom 0.9 to 1.5 wt % based on weight of the curable siliconecomposition.

It is generally known in the art how to prepare curable siliconecompositions comprising multiple ingredients including fillers. Forexample, the curable silicone composition and curable organosiloxanecomposition may be prepared by a method comprising combining theingredients such as by mixing. The ingredients may be combined in anyorder, simultaneously, or any combination thereof unless otherwise notedherein. Typically mechanics of the combining comprises contacting andmixing ingredients with equipment suitable for the mixing. The equipmentis not specifically restricted and may be, e.g., agitated batch kettlesfor relatively high flowability (low dynamic viscosity) compositions, aribbon blender, solution blender, co-kneader, twin-rotor mixer,Banbury-type mixer, mill, or extruder. The method may employ continuouscompounding equipment, e.g., extruders such as twin screw extruders(e.g., Baker Perkins sigma blade mixer or high shear Turello mixer), maybe used for preparing compositions containing relatively high amounts ofparticulates. The curable silicone composition and curableorganosiloxane composition may be prepared in batch, semi-batch,semi-continuous, or continuous process. General methods are known, e.g.,U.S. 2009/0291238; U.S. 2008/0300358.

The curable silicone composition and curable organosiloxane compositionmay be prepared as a one part or multiple part composition. The one-partcomposition may be prepared by combining all ingredients by anyconvenient means, such as mixing, e.g., as described for the method. Allmixing steps or just a final mixing step may be performed underconditions that minimize or avoid heating (e.g., maintain temperaturebelow 30° C. during mixing). The multiple part (e.g., 2 part)composition may be prepared where at least a primary organosiloxane(e.g., the diorganosiloxane such as ingredient (A)), and optionally anyother organosilicon compound (e.g., an adhesion promoter and/or chainextender/crosslinker such as the organohydrogensilicon compound ofingredient (B)), is stored in one part, and any catalyst (e.g.,ingredient (C)) is stored in a separate part, and the parts are combined(e.g., by mixing) shortly before use of the composition. Alternatively,the primary organosiloxane and any catalyst may be stored in one partand any other organosilicon compound may be stored in a separate part.Typically the chain extender/crosslinker and the catalyst are stored inseparate parts when the catalyst is catalytically active (notmicroencapsulated or not inhibited). A master batch containing theprimary organosiloxane may be prepared and stored until ready fordilution to prepare the one part. An illustrative preparation isdescribed later in the examples. The hydrocarbon vehicle and Cu—Agcore-shell particles may be stored in either part or both parts or in aseparate part.

When the curable silicone composition further comprises the MTF and theMTF is the carbon nanotubes, the carbon nanotubes may be mixed with atleast a portion of the curable organosiloxane composition to form amaster batch comprising a dispersion of the carbon nanotubes and atleast the portion of the curable organosiloxane composition. Thedispersing of the carbon nanotubes into the portion of the curableorganosiloxane composition to prepare the master batch may be carriedout by any suitable mixing means. Examples of suitable mixing means areultrasonication, dispersion mixing, planetary mixing, and three rollmilling. Alternatively or additionally, surfactants may be used tofacilitate dispersion of the carbon nanotubes in a carrier liquid (e.g.,water) to form an emulsion, which may be mixed with the curableorganosiloxane composition to give a temporary mixture, and then thecarrier liquid (e.g., water) may be removed from the temporary mixtureto give the master batch. For convenience, the carrier liquid may havehaving a boiling point from 20° to 150° C. When a surfactant is used,the carrier liquid typically is water or an aqueous mixture, but thecarrier liquid may be non-aqueous such as methanol or apolydimethylsiloxane fluid having a boiling point from 20° to 150° C.Once formed the master batch may then be mixed with the otheringredients of the curable silicone composition, including any remainingportion of the curable organosiloxane composition, to prepare thecurable silicone composition.

Once prepared the curable silicone composition and curableorganosiloxane composition may be used immediately or stored for anypractical period, e.g., ≧1 hour, alternatively ≧1 day, alternatively ≧1week, alternatively ≧30 days, alternatively ≧300 days, alternatively ≧2years before use. The curable silicone composition and curableorganosiloxane composition may be stored in a container that protectsthe curable silicone composition or curable organosiloxane compositionfrom exposure to curing conditions (e.g., heat or moisture). The storagemay be at a suitable temperature (e.g., −40°≦20° C., e.g., −30° C.) and,if desired, under an inert gas atmosphere (e.g., N₂ or Ar gas). Whendesired, curing of the curable silicone composition may be initiated byexposing it to the curing conditions to give the ECSA.

The curable silicone composition may be characterized by its owncharacteristics and/or, indirectly, by the characteristics of the ECSAprepared therefrom. For example, the curable silicone composition may becharacterizable by a curing temperature <160° C., resistance tooxidation of copper(0) of the Cu core, volume resistivity, electricallyconductivity, or any combination thereof of the ECSA.

The electrically conductive silicone adhesive (ECSA) may comprise abinder matrix comprising any cured silicone composition such as acondensation cured organosiloxane, free radical cured organosiloxane, orhydrosilylation cured organosiloxane. Curing the curable organosiloxanecomposition of the curable silicone composition yields the curedorganosiloxane binder matrix, wherein the Cu—Ag core-shell particles maybe unsintered. Some embodiments of the present invention provide theECSA as a composition of matter, which may be described as aproduct-by-process. Other embodiments provide the ECSA as a compositestructure comprising the Cu—Ag core-shell particles and MTF, if any,widely dispersed throughout a binder matrix (cured organosiloxanematrix) comprising a product of curing the curable silicone composition.The as-cured ECSA facilitate transmission of electric current as is,e.g., such that an as-cured ECSA disposed between first and secondelectrical components of an electrical device facilitates conduction ofelectric current between the first and second electrical components viathe as-cured ECSA without having to expose the electrically conductivefiller in the as-cured ECSA (e.g., without having to abrade a surface ofthe as-cured ECSA). The composite structure of the ECSA may becharacterizable by a cross-sectional image, longitudinal image, or two-or three-dimensional arrangement of the Cu—Ag core-shell particles andMTF, if any, in the binder matrix. Any carbon nanotubes may requirehigher magnification viewing to be seen in the cross-sectional imagecompared to any magnification that may be used to view the Cu—Agcore-shell particles, and/or cured organosiloxane matrix. The ECSA maybe characterized by a volume resistivity of less than 0.020 Ohm-cm,alternatively <0.0010 Ohm-cm, or any one of the aforementioned volumeresistivity values.

The ECSA may provide adhesion to a variety of different substrates suchas a metal (e.g., aluminum), a ceramic, or a silica glass substrate. Insome embodiments, surfaces of some substrates may be treated first toremove or change composition of a surface layer, which may be of adifferent material than a basal layer of the substrate. Alternatively,the same surface layer may be untreated or mechanically patterned beforebeing contacted with the curable silicone composition and/or ECSA.Examples of surface layers that might be removed, alternatively left on,are metal oxide layers, protective coatings (e.g., organic coatingsapplied to metals that are prone to oxidation when exposed to ambientair), and powders such as powder residues that may have been depositedon the substrate be mechanical etching of the substrate. Examples ofmetal substrates are the electrically conductive metals and metal alloysdescribed before, alternatively aluminum, copper, gold, niobium,palladium, platinum, silver, stainless steels, tantalum, and titanium.The surface layer of the substrate receiving the curable siliconecomposition or ECSA is a material that is capable of chemically bondingto the ECSA, which after being prepared by curing the curable siliconecomposition thereon is adhered to the material such that the adhesivestrength is achieved. The ECSA may also provide adhesion to a variety ofdifferent organic polymer substrates that have first been primed ortreated. Examples of organic polymer substrates that may be primed ortreated to form a surface thereon for adhering to the ECSA arepolyethylene and polypropylene. If the surface layer is treated(primed), the priming or treating the surface of the substrate maycomprise treating a working portion of the surface thereof with anadhesion promoter or by chemical etching, mechanical etching, or plasmatreating the working portion of the surface. Examples of suitableadhesion promoters are OFS 6040 XIAMETER, DOW CORNING P5200 AdhesionPromoter, and 1200 OS Primer Clear. Generally, increasing curingtemperature and/or curing time will improve adhesion.

Different embodiments of the ECSA may be compared by characterizingtheir adhesive strength on a same substrate material such as aparticular silica glass substrate according to the Peel Resistance TestMethod described later. When the substrate material is an unprimed oruntreated substrate, alternatively a substrate that has been previouslyprimed or treated, the ECSA may be characterizable by an adhesivestrength of at least 0.3 Newton (N) when measured on silica glasssubstrate according to the Peel Resistance Test Method. Alternatively,the ECSA may be characterizable by an adhesive strength of at least 0.1N, alternatively at least 0.3 N, alternatively at least 0.5 N,alternatively at least 1.0 N. The ECSA may have any maximum adhesivestrength. In some embodiments the ECSA may have a maximum adhesivestrength of 5 N, alternatively 2 N, alternatively 1 N, alternatively 0.3N. The adhesive strength value of a particular ECSA may vary dependingon the material of the substrate. For purposes of characterizing anembodiment of the curable silicone composition after curing as being anECSA, the substrate may be borosilicate silica glass. Different ECSAsmay be characterized or compared by their adhesive strength according tothe Peel Resistance Test Method when measured on a same substrate suchas the borosilicate silica glass substrate. The silica glass may beEagle XG silica glass (e.g., HS-20/40) from Corning Inc., Corning, N.Y.,USA.

The ECSA independently may be employed in some applications as anadhesive but not as a means for conducting electrical current. Suchapplications include using the ECSA for adhering same or differentsubstrates comprising non-electrically conductive materials to eachother. Reiterated, the use of the ECSA as an adhesive may includeapplications wherein the ECSA does not function or need to function toconduct electric current. Alternatively, the ECSA may be used in someapplications as an adhesive and, at least periodically, as a means forconducting electric current between at least two electrical componentsof an electrical device. The at least two electrical components haveopposing surfaces between which contact the ECSA. The periods duringwhich the electric current may be conducted therebetween are when theelectrical components or electrical components and electrical device areelectrically active. Alternatively, the ECSA may be employed in someapplications as a means for conducting electric current between at leasttwo electrical components of an electrical device, but not as anadhesive for adhering the electrical components to each other.Reiterated, the use of the ECSA as a means for conducting electriccurrent may between at least two electrical components of an electricaldevice may include applications where the electrical components arebeing held in electrical operative contact to the ECSA via a means otherthan adhesive action. Examples of such other non-adhesive means arewhere the electrical components are disposed in friction fit with eachother or a common housing, a mechanical fastening means such as anexternally screw-threaded fastener, solder (limited to contact with avery minor areas of the opposing surfaces of the electrical components),and a clamp.

An electrical device comprising first and second electrical componentshaving opposing surfaces and the ECSA disposed between and in adheringoperative contact with the opposing surfaces of the first and secondelectrical components; wherein the first and second electricalcomponents are disposed for electrical operative communication with eachother via the ECSA; and wherein the ECSA is characterizable by a volumeresistivity of less than 0.020 Ohm-cm, alternatively <0.0010 Ohm-cm, orany one of the aforementioned volume resistivity values. The ECSA bindsthe electrical components together and facilitates transfer of electriccurrent between them via the ECSA during operation of the electricaldevice. A wide variety of electrical devices may employ the ECSA. Theopposing surfaces of the first and second electrical components may besurfaces of an untreated substrate as described above. Alternatively,one or both of the opposing surfaces of the first and second electricalcomponents may be surfaces of substrates that may have previously beenprimed or treated to form a surface thereon for adhering to the ECSA.Examples of electrical devices that may be manufactured with the curablesilicone composition and ECSA are electrical components such as antenna,attenuators, light ballast, batteries, bimetallic strips, brushes,capacitors, electrochemical cells, control boards, instrument panels,distributors, electrographs, electrostatic generators, electronicfilters, light flashers, fuses, inductors, jacks, plugs, electrostaticprecipitators, rectifiers, relays, resistors, spark arrestors,suppressors, terminals, and electronics circuit board wiring patterns.Examples of such electrical devices also include higher order electricaldevices, which may contain a plurality of such electrical components.The higher order electrical devices include photovoltaic cell modulesand panels, and electronic devices such as computers, tablets, routers,servers, telephones, and smartphones. The use of the ECSA in theelectrical devices is not particularly limited, and for example the ECSAmay be used in place of any ECA of ad rem prior art electrical device.

A method of manufacturing the electrical device comprising the first andsecond electrical components having surfaces and the ECSA, the methodcomprising depositing the curable silicone composition onto one or bothsurfaces of the first and second electrical components, and orientingthe first and second electrical components so that their surfaces areopposing each other to give a preassembly comprising the curablesilicone composition disposed between and in physical contact with theopposing surfaces of the first and second electrical components; andcuring the curable silicone composition between the opposing surfaces ofthe first and second electrical components to give the electricaldevice. The depositing may be performed in any suitable manner. E.g., asuitable manner of the depositing comprises disposing all of the curablesilicone composition on a surface of one, but not both, of the first andsecond electrical components, and then bringing the disposed curablesilicone composition in opposing contact to the surface of the other one(i.e., the one lacking the composition) of the first and secondelectrical components to give the preassembly. Another suitable mannerof the depositing comprises disposing a first portion of the curablesilicone composition on one of the surfaces of the first and secondelectrical components, disposing a second portion of the curablesilicone composition on the other one of the surfaces of the first andsecond electrical components, and then bringing the first and secondportions of the disposed curable silicone composition in opposingcontact to give the preassembly. The first and second portions of thecurable silicone composition may be the same or different in amount,composition, batch, age, extent of curing, and/or other property (e.g.,temperature). The invention contemplates that still other suitablemanners may be used so long as the preassembly is produced therewith. Itis generally known in the art how to prepare different electricalcomponent assemblies comprising an ECSA prepared by curing a curablesilicone composition. The electrical device comprises the first andsecond electrical components and the electrically conductive siliconeadhesive disposed between and in adhering operative contact with theopposing surfaces of the first and second electrical components suchthat the first and second electrical components are disposed forelectrical operative communication with each other via the electricallyconductive silicone adhesive. The ECSA in the electrical device ischaracterizable by a volume resistivity of less than 0.020 Ohm-cm,alternatively <0.0010 Ohm-cm, or any one of the aforementioned values.The manufacturing method may comprise manufacturing more than oneelectrical device wherein curable silicone compositions having differentrheologies are employed for manufacturing different ones of theelectrical devices. For example, the method may comprise depositing afirst curable silicone composition having a first thixotropicIndex(η₁/η₁₀) onto the opposing surfaces of the first and secondelectrical components to give a first preassembly comprising the firstcurable silicone composition disposed between and in physical contactwith the opposing surfaces of the first and second electricalcomponents; and curing the first curable silicone composition betweenthe opposing surfaces of the first and second electrical components togive a first electrical device; adjusting the rheology of the firstcurable silicone composition to give a second curable siliconecomposition having a second thixotropic Index(η₁/η₁₀), wherein the firstthixotropic Index(η_(1i)/η₁₀) and second thixotropic Index(η₁/η₁₀)differ from each other by at least 0.3, alternatively at least 0.5,alternatively at least 1, alternatively at least 2, alternatively atleast 3, alternatively at least 4, alternatively at least 5, all as aresult of the adjusting; and depositing the second curable siliconecomposition onto opposing surfaces of third and fourth electricalcomponents to give a second preassembly comprising the second curablesilicone composition disposed between and in physical contact with theopposing surfaces of the third and fourth electrical components; andcuring the second curable silicone composition between the opposingsurfaces of the third and fourth electrical components to give a secondelectrical device. Each depositing step may independently be performedin any suitable manner as described before to independently give thefirst and second preassemblies. A portion of a master batch of the firstcurable silicone composition may be used in the manufacture of the firstelectrical device and another portion of the master batch of the firstcurable silicone composition may be used in the adjusting step. Thefirst electrical device may be manufactured before, alternatively afterthe adjusting step. Each of the first and second thixotropicIndex(η₁/η₁₀) values independently may be between 3 and 10. The firstand second electrical components of the first electrical device aredisposed for electrical operative communication with each other via afirst ECSA, wherein the first ECSA is prepared by the curing of thefirst curable silicone composition and is characterizable by a volumeresistivity of less than 0.020 Ohm-cm, alternatively <0.0010 Ohm-cm, orany one of the other aforementioned volume resistivity values. The thirdand fourth electrical components of the second electrical device aredisposed for electrical operative communication with each other via asecond ECSA, wherein the second ECSA is prepared by the curing of thesecond curable silicone composition and is characterizable by a volumeresistivity of less than 0.020 Ohm-cm, alternatively <0.0010 Ohm-cm, orany one of the other aforementioned volume resistivity values. Thevolume resistivity of the first and second ECSAs may be the same,alternatively may differ from each other, e.g., by <0.0001 Ohm-cm,alternatively <0.00005 Ohm-cm, alternatively <0.00002 Ohm-cm.

The manufacturing method may comprise manufacturing more than oneelectrical device wherein the depositing and/or curing conditions(collectively, manufacturing conditions) are different. For example, thedepositing and/or curing conditions may be different from each other inat least one of temperature of the curable silicone composition, rate offlow of the curable silicone composition, cure time of the curablesilicone composition, orientation of the substrate when in contact withthe curable silicone composition, and chemical composition or structureof the surfaces of the first and second substrates. The rheology may beadjusted without increasing the total concentration of electricallyconductive core such that the thixotropic index (η₁/η₁₀) values beforeand after the rheology adjustment are each between 3 and 10 and differfrom each other by at least 0.3, alternatively at least 0.5,alternatively at least 1, alternatively at least 2, alternatively atleast 3, alternatively at least 4, alternatively at least 5, all as aresult of the adjusting.

As mentioned before, in any of the foregoing embodiments, depositing thecurable silicone composition onto the opposing surfaces of the first andsecond electrical components may comprise contacting the curablesilicone composition to one or both surfaces, and bringing the surfacesinto opposition to each other so that the curable silicone compositiondirectly contacts both of the opposing surfaces. Likewise in any of theforegoing embodiments employing same, the depositing the curablesilicone composition onto the opposing surfaces of the third and fourthelectrical components may comprise contacting the curable siliconecomposition to one or both surfaces, and bringing the surfaces intoopposition to each other so that the curable silicone compositiondirectly contacts both of the opposing surfaces. The contacting of thecurable silicone composition to the surfaces may be done sequentially orsimultaneously. In the electrical device the first and second electricalcomponents sandwich the curable silicone composition between theiropposing surfaces.

The curable silicone composition may be applied to the surface(s) byvarious methods of deposition. Examples of suitable methods includeprinting through screen or stencil, dispensing, or other methods such asaerosol, ink jet, gravure, or flexographic, printing. The curablesilicone composition may be applied to the surfaces to make directphysical, adhesive and electrical contact to the first and secondelectrical components, alternatively the third and fourth electricalcomponents. Curing the applied curable silicone composition gives theECSA in direct physical, adhesive and electrical contact to the opposingfaces, and enables electrical operative communication between the firstand second electrical components, alternatively the third and fourthelectrical components, via the ECSA.

Conditions for curing typically comprise elevated temperatures leadingto the substantial removal of the hydrocarbon vehicle. Substantially allof other ingredients of the curable silicone composition are, or reactin situ to form components that are, less volatile under the curingconditions than is the hydrocarbon vehicle. Thus, the concentration ofCu—Ag core-shell particles and other ingredients besides the hydrocarbonvehicle are usually higher in the ECSA than in the curable siliconecomposition.

Depending on whether the curable organosiloxane composition iscondensation curable, free radical curable or hydrosilylation curable asdescribed earlier, conditions for the curing may further compriseexposure of the curable silicone composition to UV light, peroxides,metal-containing catalyst, and/or moisture. For example, curing thehydrosilylation-curable silicone composition typically comprises heatingthe hydrosilylation-curable organosiloxane containing thehydrosilylation catalyst to remove a substantial amount of thehydrocarbon vehicle and give the ECSA. The curing conditions mayfacilitate shrinkage of volume of material during curing and result inimproved packing of the electrically conductive filler and an ECSA withincreased electrical conductivity, decreased volume resistivity, or bothcompared to an ECSA that is the same except having a hydrocarbon vehiclewith a boiling point below 100° C. (e.g., 50° C.).

Some advantages and benefits of the present invention. The ECSA of theinvention contains a very low amount of noble metal (<15 wt % Ag), butstill demonstrates electrical resistivity below 0.020 Ohm-cm,alternatively <0.0010 Ohm-cm, or any one of the other aforementionedvolume resistivity values; and maintains its electrical performance forat least 1,000 hours under harsh environmental conditions such as dampheat 85 C/85% RH. Alternatively or additionally, as mentioned before thecurable silicone composition may be curable at a temperature less thanor equal to 160° C. This cure temperature is less than temperaturesrequired for sintering the Cu—Ag core-shell particles and less thantemperatures required for soldering conductive compositions based onmixtures of electrically conductive and solderable particles.

Alternatively or additionally, the curable silicone composition isstencil/screen printable. Also, due to the high amount of solids in it(>80 wt %), the curable silicone composition enables printing ofconductive structures with high aspect ratios. Therefore, the inventionprovides embodiments wherein the ECSA is in the shape of a stable bondline and achieves optimal electrical performance while using low totalsilver concentration, and hence lowers cost of the ECSA material forcost-sensitive applications such as photovoltaic cell modules.

Alternatively or additionally, the ECSA of this invention demonstratesprimer-less adhesion to a wide range of substrate materials.Beneficially, the ECSA also provides adequate bonding to a wide varietyof different copper foil surface finishes. Thus, the ECSA enable directand reliable electrical and mechanical contact to copper surfaces forthe lifetime of a device employing same such as a photovoltaic cellmodule. Thus, the ECSA may benefit many different electrical deviceindustries and technologies.

Alternatively or additionally, in the present invention, the carbonnanotubes are believed to have minimal or no negative effect onelectrical conductivity. While carbon nanotubes generally may impartsome electrical conductivity in a cured polymer that would otherwise notbe electrically conductive if it lacked carbon nanotubes, instead thepresent invention advantageously may employ the carbon nanotubes as aconcentration-sensitive rheology modifier in the curable siliconecomposition at concentrations where the carbon nanotubes ultimately haveno or minimal negative effect on electrical conductivity of the ECSAresulting from curing the curable silicone composition. The presentinvention provides the curable precursor composition wherein totalconcentration of silver in the composition is significantly below 15 wt% and wherein the volume resistivity of the resulting ECA can bemaintained below 0.020 Ohm-cm, alternatively <0.0010 Ohm-cm, or any oneof the other aforementioned volume resistivity values. The presentinvention advantageously found a way to successfully employ certainsecondary filler that functions in an enhancing manner in the presentcurable silicone composition and ECSA without adding other highlyelectrically conductive metal such as gold or aluminum metals, to thecurable silicone composition and ECSA. This has enabled lowering thetotal concentration of silver in a silicone binder matrix to less than15 wt % (e.g., 7.0 to 14.0 wt %) while still achieving a volumeresistivity of the curable silicone composition less than 0.020 Ohm-cm,alternatively <0.0010 Ohm-cm, or any one of the other aforementionedvolume resistivity values, without adding other highly electricallyconductive metal filler.

Alternatively or additionally, in some embodiments wherein the curablesilicone composition further contains the MTF and the MTF comprisescarbon nanotubes, the curable silicone composition may advantageously becharacterizable by a thixotropic index that is adjustable from 3 to 10(3.0 to 10.0) without increasing the total concentration of silver andCu—Ag core-shell particles, and wherein the curable silicone compositionremains curable to an ECSA having a volume resistivity of less than0.020 Ohm-cm, alternatively <0.0010 Ohm-cm, or any one of the otheraforementioned volume resistivity values, and the total concentration ofsilver in the curable silicone composition is <15 wt % (e.g., from 7.0to 12 wt %) and the curable silicone composition lacks gold;alternatively, gold and aluminum metals. In such embodiments therheology of the curable silicone composition may be adjusted over a widerange to accommodate different application requirements for makingelectrical devices wherein the volume resistivity of the resulting ECSAmay be maintained below 0.020 Ohm-cm, alternatively <0.0010 Ohm-cm, orany one of the aforementioned volume resistivity values. The manner ofadjusting of the thixotropic index may comprise adjusting the combinedwt % portion of the Cu—Ag core-shell particles and MTF carbon nanotubes;alternatively raising or lowering the concentration of carbon nanotubesin the curable silicone composition so long as the concentration remainswithin the wt % range described herein for the carbon nanotubes therein,alternatively raising or lowering the concentration of the hydrocarbonvehicle so long as the concentration of the hydrocarbon vehicle remainswithin the wt % range described herein for the hydrocarbon vehicle, or acombination of two, alternatively three thereof. Such manners ofadjusting are contemplated so long as the thixotropic index changes byat least 0.3, alternatively at least 0.5, alternatively at least 1,alternatively at least 2, alternatively at least 3, alternatively atleast 4, alternatively at least 5, all as a result of the adjusting,while the thixotropic index remains greater than 3, the totalconcentration of the electrically conductive filler does not increase,and the curable silicone composition remains curable to an ECSA having avolume resistivity of less than 0.020 Ohm-cm, alternatively <0.0010Ohm-cm, or any one of the other aforementioned volume resistivityvalues. Even when the concentration of carbon nanotubes is raised orlowered, the thixotropic index of the ECSA prepared from the curablesilicone composition may change by a significant amount (e.g., 1 ormore) while unexpectedly the volume resistivity of the resulting ECSAmay remain virtually unchanged (e.g., may change by from 0 to 0.0001,alternatively from 0 to 0.0005, alternatively from 0 to 0.00002 Ohm-cm).Further, while the thixotropic index may be adjusted in this range, thevolume resistivity of the resulting ECSA may remain virtually unchanged.Further, the present invention may achieve this advantage without usinggold, or gold and aluminum. Therefore, in some embodiments, the curablesilicone composition and ECSA composition lack gold, or gold andaluminum. Alternatively, the adjusting may be achieved without varyingconcentration of the hydrocarbon vehicle in the curable siliconecomposition, alternatively the concentration of the hydrocarbon vehiclein the curable silicone composition may be varied by itself or incombination with varying the electrically conductive filler.

Such an adjustable curable silicone composition is useful for developingdifferent curable precursor formulations that meet the varied rheologyneeds of electrical component/device manufacturing conditions whileretaining the ECSA electrical properties needed by end-users of theelectrical component/device device. For example, the curable siliconecomposition has rheology characteristics that are useful for screenprinting thereof, including for screen printing different types ofelectrical components/devices. The curable silicone composition hassufficient viscosity such that it does not exhibit too much slump,bleeding, dripping, and/or filler settling during screen printingthereof. Additionally, the curable silicone composition may not have toomuch viscosity for successful screen printing. The curable siliconecomposition has adjustable rheology in order to meet the diverse needsof manufacturers of different electrical devices such as photovoltaicdevices and electronic circuit boards while retaining the resultingECA's electrical properties needed by the device users.

Determining numerical property values: for purposes of the presentinvention and unless indicated otherwise, the numerical property valuesused herein may be determined by the following procedures.

Determining adhesive strength: for purposes of the present invention andunless indicated otherwise, a Peel Resistance Test Method that is inagreement with the test method described in ASTM D6862-04 (Standard TestMethod for 90 Degree Peel Resistance of Adhesives) has been used. PeelResistance Test Method: uses a 90-degree peel test to determine theresistance-to-peel strength of a test adhesive bonding a rigid adherent(substrate such as silica glass) and a flexible adherent (e.g., 2 mmwide Cu wire), For purposes of this test method, surfaces of theadherents do not undergo surface priming or treatment prior to adhesiveapplication thereto. Test adhesive is screen printed onto the rigidadherent through apertures of dimension 0.5 mm×114 mm×0.25 mm. Flexible2 mm wide Cu wire is placed on top of the screen printed test adhesive,and the resulting structure is heat treated at 150° C. for 15 minutes inair environment to give a test sample. The 90-degree peel resistancemeasurement takes place on a gripping fixture of an INSTRONelectromechanical testing system, which gripping fixture allows aconstant 90 degree peel angle to be maintained during the test. The testsample is positioned on the INSTRON table, and clamped down on bothsides of the test area at a distance of approx 5 mm to minimize flexure.About 3 centimeter (cm) length of the Cu wire is standing out of themeasurement zone (i.e., test area where the Cu wire contacts the rigidadherent) and is used for attaching the test sample to a pull tester.For every measurement the Cu wire is bent at a 2 mm distance from themeasurement zone and inserted into the gripping fixture. Either an endportion of the Cu wire overhangs the rigid adherent, or the end portionis pulled up by hand from the rigid adherent to debond (physicallyseparate) the end portion of the Cu wire from the rigid adherent withoutdebonding all of the Cu wire therefrom, and the debonded end portion isdisposed into the gripping fixture. The force needed to bend the Cu wireis not taken into account since only data obtained with the same type ofCu wire are compared. A 100 Newton (N; equivalent to 20 lbs) load celland a strain rate of 0.5 inch per minute (1.27 cm/minute) is used andthe average peel force over a 15 mm length of travel of the test sampleis measured. At least 4 specimens are measured for each test sample toobtain an average peel force, which is what is reported.

Determining boiling point: measure boiling point by distillation atstandard atmospheric pressure of 101.3 kilopascals (kPa).

Determining dynamic viscosity: for purposes of the present invention andunless indicated otherwise, use dynamic viscosity that is measured at25° C. using a rotational viscometer such as a BrookfieldSynchro-lectric viscometer or a Wells-Brookfield Cone/Plate viscometer.The results are generally reported in centipoise. This method is basedon according to ASTM D1084-08 (Standard Test Methods for Viscosity ofAdhesives) Method B for cup/spindle and ASTM D4287-00 (2010) (StandardTest Method for High-Shear Viscosity Using a Cone/Plate Viscometer) forcone/plate. Dynamic viscosity for purposes of determining thixotropicindex is measured according to the TI Test Method described later.

Determining kinematic viscosity: use test method ASTM-D445-11a (StandardTest Method for Kinematic Viscosity of Transparent and Opaque Liquids(and Calculation of Dynamic Viscosity)) at 25° C. Expressed in cSt ormm²/s units.

Determining state of matter: Characterize state of matter as solid,liquid, or gas/vapor at 20° C. and a pressure of 101.3 kPa.

Determining volume resistivity: The volume resistivity of ECSA testsamples reported in the Examples below was determined using thefollowing Volume Resistivity Test Method. The volume resistivity wasdetermined using a four-point-probe instrument, GP 4-TEST Pro, from GPSolar GmbH, Germany. This instrument has a line resistance probe headand incorporates Precise Keithley electronics for current sourcing andvoltage measurement. The line resistance probe head is constructed tomeasure electrical resistance through a 5 cm distance along a conductivestrip the ECSA test sample. An aliquot of the test material wasdeposited on non-conductive substrate (e.g., silica glass or ceramic) byscreen printing through apertures of dimension 5 mm×60 mm×0.25 mm. Thisformed a uniform line having an area of 5 mm×60 mm=300 mm². The spreadtest material was thermally cured by conveying it through an oven set toa temperature of 150° C. under ambient (air) atmosphere for 15 minutesto produce a test sample of the material (e.g., ECSA The voltage dropbetween the two inner probe tips was then measured at a selected currentto provide a resistance value in ohms (Ω).

The initial volume resistivity of the cured composition was calculatedusing the equation ρ=R(W×T/L) where ρ is the volume resistivity inOhm-centimeters (Ω-cm), R is the resistance in ohms (Ω) of the curedcomposition measured between two inner probe tips spaced 5 cm apart, Wis the width of the cured layer in cm, T is the thickness of the curedlayer in cm, and L is the length of the cured layer between the innerprobes in cm. The thickness of the cured layer was determined using amicrometer (Ono Sokki digital indicator number EG-225). If desired, across sectional area might be determined more accurately using a Zygo7300 white light interferometer. Even so, all of the thicknessmeasurements in the below examples were determined with the micrometer.Volume resistivity (ρ) in Ω-cm units represents the average value ofthree measurements each performed on identically prepared testspecimens. These measurements have a relative error of less than 10percent.

Determining thixotropic index (η₁/η₁₀): The thixotropic index (η₁/η₁₀)is determined using the following TI Test Method. Measure dynamicviscosity (η) in Pascal-seconds (Pa·s) at 25° C. using an ARES G2Parallel Plate Rheometer with 40 millimeter diameter plates and a gap of1 millimeter (Rheometer). Agitate a test sample for 20 seconds at 1,200revolutions per minute (rpm) with a SPEEDMIXER dual asymmetriccentrifugal laboratory mixer (model no. DAC 150 FVZ-K, Haushild & Co.KG, Hamm, Germany). Then immediately load the agitated test sample intothe Rheometer for a conditioning step and then a flow sweep step. Duringthe conditioning step, mix the test sample for 300 seconds at a shearrate of 0.001 radians per second to give a conditioned test material.Then during the flow sweep step, measure dynamic viscosity of theconditioned test material at shear rates ranging from 0.001 to 100radians per second (rad·s⁻¹ or rad/s), recording at least five datapoints per shear rate decade (i.e., record at least five data points at0.001 rad/s, at least five data points at 0.01 rad/s, etc. up to andincluding at least five data points at 100 rad/s). The thixotropic index(η₁/η₁₀) is calculated by dividing the dynamic viscosity values in Pa-sat shear rates of 1 and 10 rad/s, respectively

Determining weight percent (wt %): base weight percent of an ingredientof a composition, mixture, or the like on weights of ingredients addedto prepare, and total weight of, the composition, mixture, or the like.

Ingredients used in the examples follow.

Hydrocarbon vehicle (HV1) was an isoalkanes mixture containing 80 to 81%(C₁₆)isohexadecanes, 3% (C₁₃)isotridecanes, and 16 to 17%(C₁₂)isododecanes.

Cu—Ag core-shell particles (Cu88-Ag12) were flakes that had 12 wt % Agand 88 wt % Cu; a D90 particle size of 5.0 μm.

Cu—Ag core-shell particles (Cu90-Ag10) were spheres that had 10 wt % Agand 90 wt % Cu; a D90 particle size of 6.1 μm.

Multi-walled carbon nanotubes (MWCNT1) had an outer diameter of from 50to 100 nm and length of from 5 to 20 μm. Derivatized carbon nanotubes(DCNT1) were graphenated MWCNT that had >95 wt % purity, and an outerdiameter of from 50 to 80 nm, inner diameter of from 5 to 15 nm, and alength of from 10 to 20 μm.

Vinyl-functionalized Polydimethylsiloxane (VFPDMS1): this primaryorganosiloxanes was a vinyl-functionalized polydimethylsiloxane havingdynamic viscosity of from 40,000 to 70,000 Pa·s.

A chain extender/crosslinker was a trimethylsiloxy-terminated dimethylmethylhydrogensiloxane (CE/CL1) liquid having a dynamic viscosity of 55cSt (55 mm²/s). Another chain extender/crosslinker wasdimethylvinylsiloxy-terminated methylhydrogencyclosiloxane (CE/CL2).

Vinyl-functionalized Polydimethylsiloxane (VFPDMS2): this primaryorganosiloxanes was a vinyl-functionalized polydimethylsiloxane havingdynamic viscosity of from 5,000 to 15,000 Pa·s.

Adhesion promoter 1 (AP1) was an a 3:2 (wt/wt) mixture ofbis(alpha,omega-glycidoxyalkyl)-dialkyl/(alkyl,alkenyl)siloxane adhesionpromoter with a kinematic viscosity of 17 cSt (17 mm²/s) andbis(alpha,omega-glycidoxyalkyl-D3 to D6 alkyl,hydrogencyclosiloxane),wherein there are two bis(alpha,omega-glycidoxyalkyl-D3 to D6organo,hydrogencyclosiloxanyl moieties, which are linked to each othervia an alkylene-dialkylsiloxanyl-alkylene linker.

Adhesion promoter 2 (AP2) was bis(alpha,omega-glycidoxymethyl-D3 to D6methyl,hydrogencyclosiloxane) with dynamic viscosity of 0.10 to 0.15Pa·s.

Catalyst (CAT1) was a microencapsulated platinum catalyst in the form ofshell-core particles, wherein CAT1 contained 0.008 wt % Pt, wherein theencapsulant or shell was a cured vinyl-terminated polydimethylsiloxaneand the core comprised a platinum-ligand complex.

Non-limiting examples of the invention follow. They illustrate somespecific embodiments and aforementioned advantages. The inventionprovides additional embodiments that incorporate any one limitation,alternatively any two limitations, of the Examples, which limitationsthereby may serve as a basis for amending claims.

Preparation Method: The curable silicone compositions of the exampleswere prepared by mixing the Vinyl-functionalized Polydimethylsiloxane 1or Vinyl-functionalized Polydimethylsiloxane 2 and any multi-walled CNTsor treated CNTs, if used, (or other MTF) to form a master batch (MB1).Mixing to form MB1 was done with an EXAKT Three Roll Mill (model no.80E, Exakt Advanced Technology) in 5 passes using a 5 to 70 μm gap at 30revolutions per minute (rpm). To a pot of a 0.5 liter planetary mixer(Custom Milling and Consulting, Fleetwood, Pa., USA) add HV1; AP1; AP2,if any; Cu—Ag1; an aliquot of MB1 if CNTs are used; andVinyl-functionalized Polydimethylsiloxane 1; and mix resulting contentsfor 5 minutes at 15 Hertz and 5 minutes at 30 Hertz to wet-out anddisperse electrically conductive filler to give a precursor mixture. Tothe precursor mixture add the chain extender/crosslinker CE/CL1 (or bothCECL1 and CE/CL2) and the microencapsulated platinum catalyst (CAT1),and mix gently to prevent heating, and de-air the pot to give a curablesilicone composition of any one of Examples 1 to 11. The amounts of theingredients of the hydrosilylation-curable organosiloxane and thecurable silicone composition prepared therefrom were chosen so as togive the wt % concentrations listed below in Tables 1 and 2,respectively.

TABLE 1 Hydrosilylation-curable organosiloxane compositions - Examples 1to 19. Primary organo- Ex. siloxane CE/CL1 AP1 AP2 CAT1 No. (wt %) (wt%) (wt %) (wt %) (wt %) 1 VFPMDS1 0.7 0.7 0 1.4 (7.2 wt %) 2 VFPMDS1 0.20.7 0.5 1.4 (6.4 wt %) 3 VFPMDS1 0.2 0.7 0.5 1.4 (6.6 wt %) 4 VFPMDS10.2 0.7 0.5 1.4 (6.4 wt %) 5 VFPMDS1 0.4 0.7 0 1.4 (7.4 wt %) 6 VFPMDS20.4 0.7 0 1.4 (7.4 wt %) 7 VFPMDS1 0.4 0.7 0 1.4 (7.4 wt %) 8 VFPMDS10.4 0.7 0 1.3 (6.8 wt %) 9 VFPMDS1 0.4 0.7 0 1.4 (7.4 wt %) 10 VFPMDS10.6 1.1 0 2.1 (11.1 wt %) 11 VFPMDS1 0.6 1.1 0 2.1 (11.1 wt %) 12VFPMDS1 0.2 0.7 0.5 1.4 (6.4 wt %) 13 VFPMDS1 0.2 0.7 0.5 1.4 (6.5 wt %)14 VFPMDS1 0.2 0.7 0.5 1.4 (6.4 wt %) 15 VFPMDS1 0.2 0.7 0.5 1.4 (6.8 wt%) 16 VFPMDS1 0.2 0.7 0.5 1.4 (6.4 wt %) 17 VFPMDS1 0.3 1.2 0.8 2.3(10.7 wt %) 18 VFPMDS1 0.2 0.7 0.5 1.4 (6.4 wt %) 19 VFPMDS1 0.3 1.2 0.82.3 (10.7 wt %)

TABLE 2 Curable silicone compositions - Examples 1 to 11. Core-ShellThixotropic Hydro- Particles Filler carbon Organo- Ex. Cu88—Ag12 MWCNTsVehicle siloxane* Other No. (wt %) (wt %) (wt %) (wt %) (wt %) 1 85 0.85 10.0 0 2 80 0.8 10 10.0 0 3 82 0.8 8 10.0 0 4 85 0.8 5 9.2 0 5 80 0 1010.0 0 6 85 0 5 10.0 0 7 85 0 5 10.0 0 8 85 0.8 5 9.2 0 9 85 0 5 10 0 1080 0 5 15 0 11 75 0 10 15 0 *See Table 1 unless noted otherwise.

TABLE 2.1 Curable silicone compositions using alternate thixotropicfiller. - Examples 12 to 15. Core-Shell Hydro- Particles Thixotropiccarbon Organo- Ex. Cu88—Ag12 Filler Vehicle siloxane* Other No. (wt %)(wt %) (wt %) (wt %) (wt %) Carbon Black 12 85 0.8 5 9.2 0 13 85 0.7 59.3 0 Fumed Silica 14 85 0.8 5 9.2 0 15 85 0.4 5 9.6 0

TABLE 2.2 Comparative Example - Curable silicone compositionssubstituting non-core-shell metal particle mix. Metal filler (wt %)(Filler Thixotropic Hydro- mixture contains Filler carbon Organo- Ex.88% pure Cu and MWCNTs Vehicle siloxane* Other No. 12% pure Ag) (wt %)(wt %) (wt %) (wt %) 16 85 0.8 5 9.2 0 17 75 1.3 8.3 15.4 0

TABLE 2.3 Comparative Example - Curable silicone compositionssubstituting non-core-shell, i.e. cure. Cu metal oarticles. Non-Thixotropic Hydro- Core- Filler carbon Organo- Ex. Shell Cu MWCNTsVehicle siloxane* Other No. Particles (wt %) (wt %) (wt %) (wt %) 18 850.8 5 9.2 0 19 75 1.3 8.3 15.4 0

The curable silicone compositions (CSCs) of Examples 1 to 19 may bedirectly characterized by thixotropic index and indirectly bycharacterizing the ECSA resulting from curing the CSCs by placing themfor 15 minutes in an oven set to 150° C. The ECSA may be characterizedby, for example, volume resistivity (ρ) and Thixotropic Index(η₁/η₁₀).These characterizations are shown below in Table 3.

TABLE 3 Direct characterizations of ECSAs prepared by curing the curablesilicone compositions (CSC) of Examples 1 to 19. ECSA Ex. CSC (CSC) TIECSA ρ No. Ex. No. (η₁/η₁₀) (Ohm-cm) A 1 3 to 10 0.00055 B 2 3 to 100.00047 C 3 3 to 10 0.00050 D 4 4 to 4.5 0.0004 E 5 N/R 0.00083 F 6 N/R0.00042 G 7 N/R 0.00045 H 8 4 to 4.5 0.0004 I 9 N/R 0.00050 J 10 N/R0.013 K 11 N/R 0.0082 L 12 2 to 2.5 0.000080 M 13 2 to 2.5 0.000080 N 143.5 to 4 0.000078 O 15 2.5 to 3 0.000078 P 16 5 to 5.5 1.070 Q 17 6 to6.5 0.109 R 18 5 to 5.5 0.129 S 19 5 to 5.5 0.251 CSC = curable siliconecomposition; ECSA = electrically conductive silicone adhesive; N/R meansnot reported.

As illustrated by the foregoing examples and described above, the totalsilver concentration may be kept below 15 wt %, e.g., from 9 to <11 wt %and yet the volume resistivity of the resulting ECSA remains below 0.020Ohm-cm, alternatively <0.0010 Ohm-cm, alternatively <0.00090 Ohm-cm,alternatively <0.00080 Ohm-cm, alternatively <0.00070 Ohm-cm,alternatively <0.00060 Ohm-cm, alternatively <0.00050 Ohm-cm,alternatively <0.00040 Ohm-cm. In some embodiments, the thixotropicindex of the curable silicone composition may be adjusted in the rangefrom 3 to 10, alternatively from 4 to 10 (e.g., 3.8 to 9) by employingan MTF that is carbon nanotubes and varying concentration of carbonnanotubes within a range of from 0.1 to 2 wt % (e.g., from 0.60 to 1.0wt %). The foregoing wt % values are based on weight of the curablesilicone composition. Embodiments of the present invention methodinclude such adjusting.

Examples 16-19 illustrate that the Core-shell nature of the filler iscritical to reach low resistivity and is an important feature of thepresent invention. More specifically, examples 16 and 17 comprise pure(non-Core Shell) Cu particles but also pure Ag, and the mixture betweenCu filler and Ag filler is chosen such that the Cu-to-Ag ratio is 88 to12, the same Cu-to-Ag ratio as in examples 1 to 15. Yet, compositions 16and 17 result in very high resistivity above 0.1 Ohm-cm whereasresistivities for examples 1 to 15 are well below 0.02 Ohm cm.Similarly, Examples 18 and 19 give evidence that taking a pure Cuparticle filler instead of a core-shell AgCu particle as in theinvention results in a very high resistivity above 0.1 Ohm-cm.Comparison of examples 16 and 17 on one hand and examples 18 and 19 onthe other hand show that the high resistivity is not due to the totalabsence of Ag.

The below claims are incorporated by reference here as correspondinglynumbered aspects except where “claim and “claims” are rewritten as“aspect” and “aspects.”

What is claimed is:
 1. A curable silicone composition comprising acurable organosiloxane composition, copper-silver (Cu—Ag) core-shellparticles, a mechanical thixotropic filler that is carbon nanotubes, andhydrocarbon vehicle; the curable silicone composition beingcharacterized by: a concentration of the Cu—Ag core-shell particles offrom 70 to 89 weight percent and a total concentration of silver of from7 to 14 weight percent, all based on weight of the curable siliconecomposition; wherein the composition remains curable to an electricallyconductive silicone adhesive having a volume resistivity of less than0.020 Ohm-centimeter measured according to Volume Resistivity TestMethod; and wherein the curable silicone composition is characterized bya Thixotropic Index (η₁/η₁₀) of from 3 to
 10. 2. A curable siliconecomposition comprising a blend of the following ingredients: ahydrocarbon vehicle at a concentration of from 4 to 20 weight percentbased on weight of the curable silicone composition, wherein thehydrocarbon vehicle is characterized by a boiling point from 100 to 360degrees Celsius; a curable organosiloxane composition at a concentrationof from 7 to 10 weight percent based on weight of the curable siliconecomposition; Cu—Ag core-shell particles at a concentration of from 70 to89 weight percent based on weight of the curable silicone composition;and a mechanical thixotropic filler; wherein the total concentration ofsilver is from 7 to 14 weight percent based on weight of the curablesilicone composition; wherein the composition remains curable to anelectrically conductive silicone adhesive having a volume resistivity ofless than 0.020 Ohm-centimeter measured according to Volume ResistivityTest Method; and wherein the curable silicone composition ischaracterized by a Thixotropic Index(η₁/η₁₀) of from 3 to
 10. 3. Thecurable silicone composition of claim 2 characterized by a volumeresistivity less than 0.0010 Ohm-centimeter measured according to VolumeResistivity Test Method.
 4. The curable silicone composition of claim 2characterized by the following limitations: wherein the hydrocarbonvehicle is an alkanes mixture of different molecules wherein the lowestboiling molecules have an initial boiling point greater than 150 degreesCelsius and the highest boiling molecules have an end boiling less than300 degrees Celsius and the hydrocarbon vehicle is at a concentration offrom 4 to 15 weight percent based on weight of the curable siliconecomposition; wherein the curable organosiloxane composition comprises atleast one diorganosiloxane compound, a catalyst, and an adhesionpromoter; wherein the at least one diorganosiloxane compound has onaverage per molecule at least 1 reactive moiety, wherein each reactivemoiety independently is an alkenyl moiety, Si—H moiety, Si—OH moiety,Si—OR moiety, wherein R is (C₁-C₁₀)hydrocarbyl,—C(O)(C₁-C₁₀)hydrocarbyl, or —N═CR¹R², wherein each of R¹ and R²independently is (C₁-C₁₀)hydrocarbyl or R¹ and R² are taken together toform a (C₂-C₁₀)hydrocarbylene; and wherein the at least onediorganosiloxane compound is at least 50 weight percent of the curableorganosiloxane composition; wherein the Cu—Ag core-shell particles areunsintered and are at a concentration of from 75 to 89 weight percentbased on weight of the curable silicone composition; wherein n the totalconcentration of silver is from 7.1 to 12 weight percent based on weightof the curable silicone composition; wherein the mechanical thixotropicfiller is carbon nanotubes, wherein the carbon nanotubes are at aconcentration of from 0.1 to 5.0 weight percent based on weight of thecurable silicone composition; and wherein the curable siliconecomposition is characterized by a volume resistivity less than 0.0010Ohm-centimeter measured according to Volume Resistivity Test Method. 5.The curable silicone composition of claim 4, characterized by thefollowing limitations: wherein the hydrocarbon vehicle is an alkanesmixture; wherein the curable organosiloxane composition comprises atleast one diorganosiloxane compound, at least one organohydrogensiliconcompound, a hydrosilylation catalyst, and an epoxy-functional adhesionpromoter; wherein the at least one diorganosiloxane compound has onaverage per molecule at least 1 alkenyl moiety and theorganohydrogensilicon compound has on average per molecule at least 1Si—H moiety; and wherein the at least one diorganosiloxane compound isfrom 60 to 80 wt % of the curable organosiloxane composition; whereinthe Cu—Ag core-shell particles are at a concentration of from 79.5 to86.4 weight percent based on weight of the curable silicone composition;wherein the total concentration of silver is from 7.5 to 12 weightpercent based on weight of the curable silicone composition; and whereinthe carbon nanotubes are single-walled carbon nanotubes, multi-walledcarbon nanotubes, derivatized carbon nanotubes or a combination of anytwo or more of the single-walled carbon nanotubes, multi-walled carbonnanotubes, and derivatized carbon nanotubes; and the concentration ofcarbon nanotubes is from 0.2 to 2 weight percent based on weight of thecurable silicone composition.
 6. The curable silicone composition ofclaim 5, characterized by the following limitations: wherein the alkanesmixture is an isoalkanes mixture comprising at least two of(C₉-C₁₂)isoalkanes, at least two of (C₁₂-C₁₆)isoalkanes or at least twoof (C₁₆-C₂₂)isoalkanes and the hydrocarbon vehicle is at a concentrationof from 4.5 to 15 weight percent based on weight of the curable siliconecomposition; wherein the curable organosiloxane composition ishydrosilylation curable and comprises the at least one diorganosiloxanecompound, the at least one trimethylsiloxy-terminated dimethylorganohydrogensilicon compound, a microencapsulated hydrosilylationcatalyst, and abis(alpha,omega-glycidoxyalkyl)-dialkyl/(alkyl,alkenyl)siloxane; whereinthe alkenyl of the diorganosiloxane is vinyl and the at least onediorganosiloxane compound has on average per molecule at least 1.1 vinylmoieties, the at least one trimethylsiloxy-terminated dimethylorganohydrogensilicon compound is and has on average per molecule atleast 1.1 Si—H moieties, or the least one diorganosiloxane compound hason average per molecule at least 1.1 vinyl moieties and the at least oneorganohydrogensilicon compound has on average per molecule at least 1.1Si—H moieties; wherein the at least one diorganosiloxane compound havingvinyl moieties is from 70 to 75 wt % of the curable organosiloxanecomposition; wherein the at least one trimethylsiloxy-terminateddimethyl organohydrogensilicon compound is from 1 to 5 weight percent,the microencapsulated hydrosilylation catalyst is from 10 to 15 weightpercent, and thebis(alpha,omega-glycidoxyalkyl)-dialkyl/(alkyl,alkenyl)siloxane is from5 to 10 weight percent, and together the organohydrogensilicon compound,microencapsulated hydrosilylation catalyst, and thebis(alpha,omega-glycidoxyalkyl-D3 to D6 alkyl,hydrogencyclosiloxane arefrom 20 to 30 wt % of the curable organosiloxane composition; whereinthe Cu—Ag core-shell particles are at a concentration of from 79.9 to 86weight percent based on weight of the curable silicone composition;wherein the total concentration of silver is from 7.5 to 12 weightpercent based on weight of the curable silicone composition; and whereinthe carbon nanotubes are multi-walled carbon nanotubes at aconcentration of from 0.50 to 1.5 weight percent based on weight of thecurable silicone composition; and wherein the curable siliconecomposition is characterized by a volume resistivity less than 0.00090Ohm-centimeter measured according to Volume Resistivity Test Method. 7.An electrically conductive silicone adhesive that is a product of curingthe curable silicone composition of claim 2, wherein the electricallyconductive silicone adhesive is characterized by a volume resistivity ofless than 0.0010 Ohm-centimeter measured according to Volume ResistivityTest Method, wherein some of the hydrocarbon vehicle remains in theelectrically conductive silicone adhesive after curing such that theelectrically conductive silicone adhesive has less than 5 weight percentof the hydrocarbon vehicle.
 8. An electrical device comprising first andsecond electrical components having opposing surfaces and theelectrically conductive silicone adhesive of claim 7 disposed betweenand in adhering operative contact with the opposing surfaces of thefirst and second electrical components, wherein the first and secondelectrical components are disposed for electrical operativecommunication with each other via the electrically conductive siliconeadhesive, wherein the electrically conductive silicone adhesive ischaracterized by a volume resistivity of less than 0.0010 Ohm-centimetermeasured according to Volume Resistivity Test Method.
 9. A method ofmanufacturing an electrical device comprising first and secondelectrical components having surfaces and an electrically conductivesilicone adhesive, the method comprising depositing the curable siliconecomposition of claim 2 onto one or both surfaces of the first and secondelectrical components, and orienting the first and second electricalcomponents so that their surfaces are opposing each other to give apreassembly comprising the curable silicone composition disposed betweenand in physical contact with the opposing surfaces of the first andsecond electrical components; and curing the curable siliconecomposition between the opposing surfaces of the first and secondelectrical components to give an electrical device comprising the firstand second electrical components and an electrically conductive siliconeadhesive disposed between and in adhering operative contact with theopposing surfaces of the first and second electrical components suchthat the first and second electrical components are disposed forelectrical operative communication with each other via the electricallyconductive silicone adhesive, wherein the electrically conductivesilicone adhesive is characterized by a volume resistivity of less than0.020 Ohm-centimeter measured according to Volume Resistivity TestMethod and wherein some of the hydrocarbon vehicle remains in theelectrically conductive silicone adhesive after curing such that theelectrically conductive silicone adhesive has less than 5 weight percentof the hydrocarbon vehicle.
 10. A curable silicone compositioncomprising a blend of the following ingredients: an isoalkanes mixturecomprising at least three of (C₁₂-C₁₆)isoalkanes of different moleculeswherein the lowest boiling molecules have an initial boiling point ofgreater than 210 degrees Celsius and the highest boiling molecules havean end boiling point of less than 270 degrees Celsius and thehydrocarbon vehicle is at a concentration of from 4.5 to 12 weightpercent based on weight of the curable silicone composition; ahydrosilylation-curable polydimethylsiloxane composition comprising atleast one vinyl-functional polydimethylsiloxane compound having onaverage per molecule at least 1 vinyl moieties, at least onetrimethylsiloxy-terminated dimethyl methylhydrogensilicon compoundhaving on average per molecule at least 1.1 Si—H moieties, amicroencapsulated platinum hydrosilylation catalyst, andbis(alpha,omega-glycidoxyalkyl)-dialkyl/(alkyl,alkenyl)siloxane, andbis(alpha,omega-glycidoxyalkyl-D3 to D6 alkyl,hydrogencyclosiloxane; andwherein the vinyl-functional polydimethylsiloxane compound is from 70 to75 weight percent, the trimethylsiloxy-terminated dimethylmethylhydrogensilicon compound is from 1 to 5 weight percent, themicroencapsulated hydrosilylation catalyst is from 10 to 15 weightpercent, thebis(alpha,omega-glycidoxyalkyl)-dialkyl/(alkyl,alkenyl)siloxane is from1 to 10 weight percent, and the bis(alpha,omega-glycidoxyalkyl-D3 to D6alkyl,hydrogencyclosiloxane is from 0 to 7 weight percent, all of thecurable polydimethylsiloxane composition; and wherein together thetrimethylsiloxy-terminated dimethyl methylhydrogensilicon compound,microencapsulated hydrosilylation catalyst, and thebis(alpha,omega-glycidoxyalkyl)-dialkyl/(alkyl,alkenyl)siloxane, andbis(alpha,omega-glycidoxyalkyl-D3 to D6 alkyl,hydrogencyclosiloxane arefrom 20 to 30 wt % of the curable organosiloxane composition; Cu—Agcore-shell particles are at a concentration of from 79.9 to 86.0 weightpercent based on weight of the curable silicone composition; wherein thetotal concentration of silver is from 7.5 to 12 weight percent based onweight of the curable silicone composition; and Carbon nanotubes at aconcentration of from 0.50 to 1.2 weight percent based on weight of thecurable silicone composition; and wherein the curable siliconecomposition is characterized by a volume resistivity less than 0.00090Ohm-centimeter measured according to Volume Resistivity Test Method. 11.The curable silicone composition of claim 10, wherein the curablesilicone composition is characterized by a Thixotropic Index(η₁/η₁₀) offrom 3 to 10.